We’ll omit CP6/Evolutions because it isn’t out yet, and it’s also a bit of an outlier for the rest of the series.
Best XY Set:
Worst XY Set:
Best Overall Card:
Best Full Art Card:
Worst Full Art Card:
Best EX Card:
Worst EX Card:
Best M EX Card:
Worst M EX Card:
Most Underrated Card:
Most Overrated Card:
Here’s my choices:
Best XY Set: XY7
Worst XY Set: XY8
Best Overall Card: Suicune XY8 holo.
Best Full Art Card: Gengar EX XY5 /Lugia EX XY7 tied. Honourable mentions go to Rayqyaza EX XY6, all 3 eeveeloutions and both Alakazam EX and its mega from XY 10.
Worst Full Art Card: XY8 mewtwo gold border UR cards.
Best EX Card: Giratina EX XY7
Worst EX Card: Magnezone EX XY2
Best M EX Card: M Charizard XY2 (blue one)
Worst M EX Card: M Glailie XY8
Most Underrated Card: Kyogre EX FA XY5
Most Overrated Card: Shaymin EX XY6, I know it’s playable so it’s hyped but it’s such an ugly card from a collectors standpoint!
Best Set-Fates Collide
Worst Set-Furious Fists
Best Overall card-Alakazam EX FA SR
Best Full Art Card-M Rayquaza (RS)
Worst Full Art Card-Emolga
Best Ex Card-Volcanion EX
Worst EX Card-Mewtwo EX (61/162)
Best M EX Card-M Charizard X SR
Worst M EX Card-M Manectric Ex
Most Underated Card-Skarmory EX
Most Overated Card-Shaymin EX
Ooh, I love this. Great topic Scott 
I’ll add some reasoning below so you guys know why I made my choices.
Best XY Set: XY6 Emerald Break
Contains one of my favorite Pokemon (Rayquaza) and also doesn’t suffer from “Flashfire syndrome” where you either pull Charizards or you pull jack shit. Latios/M Latios and Gallade/M Gallade make amazing additions to this set, had some of the best full art artwork in the XY series, and had a really cohesive theme throughout.
Worst XY Set: XY10 Awakening of the Psychic King
Alakazam is great, and I was hyped as anyone else for this set, but it just seems underwhelming. The full art for M Alakazam is terrible, and there was really no theme at all to this set. Seems like they threw in Altaria as a Mega for no reason, and the English set is so jumbled with the additions of 2 Japanese decks its ridiculous. Boring BREAKs, underwhelming EXs, just a bad set in my opinion.
Best Overall Card: M Rayquaza-EX FA
Probably no card will ever come close to reaching the hype level I had for this card. Anyone remember these were going for like $75 in Japanese at one point? I bought mine for $65 right after the set came out and I still have no regrets. It’s not the best design, but it creates a feeling in me that no other card does from the XY era.
Best Full Art Card: Ho-Oh-EX
A perfect full art card. Beautiful, colorful artwork and it’s not too busy. I still can’t find anything wrong with it gives the Dragons Exalted copy a run for its money.
Worst Full Art Card: M Alakazam-EX FA (most underwhelming)
y so many spoons tho…y the background brown…
Best EX Card: Rayquaza-EX (Colorless)
I just love the artwork on this and how it seems to take up the whole card. In an era of vomit-inducing, eye-bleaching, gag-reflex-triggering Yoshinob EX cards, this one was a welcome difference.
Worst EX Card: Toxicroak-EX
Imagine you’re a kid and you go in and buy 5 packs of Flashfire with your allowance money from toiling around the house doing chores. You open them up and on the last pack you spy a glitter in the back! Is it a secret rare Mega Charizard?!? Maybe one of the TWO regular Charizards?! Nope, its a Toxicroak. Your dreams are crushed.
Best M EX Card: M Gengar-EX (Shiny - Pokemon Center Halloween Promo)
The megas were all pretty crappy but this one did the lettering so well. I feel like having “HOLLOW GEIST” stretching down the card just made it so much cooler, a perfect reminder of the Halloween season it was distributed in.
Worst M EX Card: M Heracross-EX
Terrible artwork, terrible attack, I’d rather pull a regular Heracross-EX than the Mega.
Most Underrated Card: Lysandre’s Our honorable president Card (Full Art)
With it being banned you don’t see much of it anymore, but I think it’s got the best FA Supporter artwork of the XY series. That effect was so game-breaking as well, really changed the meta for the short time it was allowed.
Most Overrated Card: M Charizard-EX (Flashfire, both versions)
I’m not a fan of the artwork (especially on the Y version) and I think everyone is overrating these cards way too much. The M Charizard in Generations looks so much cooler, and assuming we get a FA version in CP6 then that would be even more epic. They are Charizards, but even in the XY series there are better Charizards.
you need to add favorite card to this lost as well.
Fuck everything else, these are facts right here. Lock the thread aye?
Best XY Set: XY6, awesome set with EX Deoxys vibes
Worst XY Set: XY8, this just didn’t have anything interesting + beginning for BREAK cards
Best Overall Card: Rayquaza EX/M Rayquaza EX from XY6
Best Full Art Card: XY5 Kyogre EX FA or XY7 Lugia EX FA
Worst Full Art Card: XY1 Emolga EX FA
Best EX Card: XY10 Kingdra EX, looks actually better than FA version
Worst EX Card: XY2 Magnezone EX
Best M EX Card: XY6 M Rayquaza EX ( colorless )
Worst M EX Card: XY8 M Mewtwo EX’s
Most Underrated Card: XY7 Tyranitar EX FA, almost too much negativity towards this card
Most Overrated Card: XY2 M Charizard EX’s and XY6 Shaymin EX, especially interested to see what happens with Shaymin’s pricing once XY6 rotates out
@hisoka107 - Favourite is what I mean by Best.
Best XY Set: XY 7, but XY 12 looks pretty cool too so we’ll see
Worst XY Set: XY 11. Just…no.
Best Overall Card: Vaporeon EX
Best Full Art Card: Kingdra EX
Worst Full Art Card: Guardevoir EX from XY 11. Just becuase it’s almost the same as the one from XY 5…
Best EX Card: Well. Vaporeon again.
Worst EX Card: Guardevoir Ex from XY 11
Best M EX Card: M Altaria EX
Worst M EX Card: M Glalie EX. Just not really creative
Most Underrated Card: No idea wich cards are underrated really
Most Overrated Card: Shaymin Ex.
Best XY Set: XY4
Worst XY Set: XY1
Best Overall Card: Alakazam Secret Rare
Best Full Art Card: Ho-Oh
Worst Full Art Card: Emolga
Best EX Card: Kingdra
Worst EX Card: Manaphy
Best M EX Card: M Beedrill
Worst M EX Card: M Heracross
Most Underrated Card: Giovanni’s Scheme FA
Most Overrated Card: Rayquaza FA Roaring Skies
Xy Was dissapoiting to say the least, because There was far too much Computer Generated shite.
Bring back the dam illustrations and proper layout for Ultra rares because every UR was a pile of cinders. BW had it right - Old layout with rectangle square box, and proper illustratored artwork, with the neo 4 shining effect on the pokemon but gliterally style. Cant be beaten, will never be forgotten.
Best XY Set: X7 … god this SET WAS AMAZING!!! Most funnest set ever, JUst kept on pulling full arts, and ON my last box the card that I wanted most from the set - Secret Rare MEga Tyranitar Full art was pulled!!! I was gonna save it, luckil;y i didnt.
Worst XY Set: XY6 … THIS SET GAVE ME NIGHTMARES!!! I ORDERED THIS FOR MY BIRTHDAY, AND WE PULLED 6 FULL ART TRAINERS!!! F*** U WALLY! So I have to disagree with you @fourthstartcg . It was very much a xy2 situation for me.
Best Overall Card: Id probably have to say ULTRA GOLDEN BOARDED Rayquaza!!! That thing was so amazing when i saw the leaks, but once in real life was so… kewl as to.
Best Full Art Card: Man this is really hard… There was some amazing ones, But Gengar full art XY4 really did it for me, and Xerneus was super kewl to.
Worst Full Art Card: Emolga is a given @milhouse , well done… But I really hated Magnezone and wally to.
Best EX Card: Lugia and Kyurem from xy7 are very hard to decide between… Even if there was a bunch of computyyer generated crap hanging around them.
Worst EX Card: Venusaur, blastoise, and charizard ex looked like crap i reckon, there faces way to big for me.
Best M EX Card: I Think they did a decent job on the xy8 mega mewtwos.
Worst M EX Card: hmmmmmmmmmmmm undecided
I still can never forgive them for what they have done the the old layout, and reduced it to a mear holo… Its unacceptable, and the ex’s are complete trash, and hopefully it changes and we get them back how they were in pcg/adv… But I doubt it.
Something different has to happen guys, no more INSANE AMOUNTS of computer generated shit all over the cards… Esepecially the ex’s… Full arts must be kept. there a given… But the Ultra RARES, have to change to the BW layout always I will have to throw tingz.
I have to say… The cp6 is looking to be my favourite set of them all… You cannot beat the old base set, and the gold cards they have chosen/full arts to omit into this set is nice. It shall be my favourite set of xy for sure…
Best XY Set: XY5 / Primal Clash - Of all the XY sets, this one felt like it was the most cohesive with its theme. I’ve mentioned it elsewhere as well, but the Pokemon EX selection blows every other set away. Groudon, Kyogre, Camerupt, Sharpedo, Gardevoir, and Aggron - what better choices are there to represent a return to Hoenn?
Worst XY Set: XY8 / Breakthrough - Nothing but Mewtwo spam and the introduction of terrible BREAK cards which stole possible EX slots. This set encompasses my main complaint about the XY era: it relied way too heavily on throwbacks to Gen 1 (and to a lesser extent 3) while many brand new Gen 6 Pokemon got put in the backseat. I am concerned that Gen 7 is going to be a repeat of this with Alolan forms of Gen 1 Pokemon overshadowing the new guys; to me this is a sign that the new designs are weak if rehashes of old ones can outmarket them.
Best Full Art Card: Ho-Oh EX Full Art - This card’s art speaks for itself really. And with me being partial for Gen 2/Johto, it was an easy choice. XY9 also is a close runner-up for best set IMO.
Worst Full Art Card: Xerosic. Out of all the characters to choose, why this guy? Why not any gym leader or E4 member? Or better yet, Champion Diantha! Worst Pokemon Full Art would be Toxicroak.
Best EX Card: Kingdra EX - Wasn’t really impressed by any regular EXs to be honest. Out of all my personal favorite Pokemon that were featured as EXs (Ampharos, Tyranitar, Espeon to name a few), this is the only regular EX I can say I was satisfied with.
Worst EX Card: Thundurus EX - It would be Toxicroak again, but I decided to not pick on it too much.
Best M EX Card: M Ampharos EX. Again, I am partial for the Pokemon, but at the same time, the colors on this card are wonderful. One of the few times I can honestly say I like the normal version over the full art.
Worst M EX Card: M Altaria EX - Only because I feel like they dropped the ball on this one. I had such high expectations for this card when it was first announced, but words would not be able to describe my disappointment when I saw the card had more attack text than Altaria on it.
Most Underrated Card: Ho-Oh - XY153 (English) / 224/XY-P (Japanese) - Probably kind of biased once again, but this holo and its Lugia counterpart were amazing enough for me to buy just for the art, and I can’t say that about any other card.
Most Overrated Card: Any Mewtwo/Gardevoir/Charizard. Seriously, did we need so many?
Best Overall Card: Saved this question for last, looked at my options, and I still can’t come up with a satisfactory answer. There’s just so many to choose from and I don’t feel like any one card flat out trumps every other. Instead, I’ll name some honorable mentions that didn’t make my best picks but still gave them a run for their money.
Best XY Set: I can’t decide between Primal Clash, Roaring Skies and Ancient Origins. All those sets had great EX / FA cards and Hoenn Pokemon were on big role on all of these sets. Despite the quality problems with English Primal Clash I just love that set. I really loved the look of Ancient Trait cards as well and I wish those would have been around for longer. Pulling Ancient Trait felt like I wasn’t pulling that much garbage because the artwork was so great.
Worst XY Set: Flash Fire simply because there’s nothing else to pull than Charizards. I wasn’t a big fan of Furious Fists and BREAKPoint as well.
Best Overall Card: Colorless Rayquaza EX and newly released Rayquaza Promo from Steam Siege blister
Best Full Art Card: Ho-Oh EX FA, Gardevoir EX FA Secret Rare
Worst Full Art Card: M Altaria EX. I’m happy I haven’t pulled this derpy face. Thankfully the basic Altaria EX FA is pretty
Best EX Card: Colorless Rayquaza EX and Xerneas EX Promo (the first one, not the shiny one)
Worst EX Card: Kangaskhan EX, Malamar EX, Glalie EX. And… Seismitoad EX. Ugh. Hate that one (mainly because of the TCG)
Best M EX Card: M Ampharos EX, M Charizard EX (Generations), M Gardevoir EX (Steam Siege), M Salamence EX
Worst M EX Card: M Altaria EX
Most Underrated Card: Difficult to say really
Most Overrated Card: Shaymin EX Roaring Skies, Seismitoad EX (ofc good in TCG, I know),
Best XY Set: Roaring Skies
Worst XY Set: Phantom Forces
Best Overall Card: Full Art Mega Rayquaza Roaring Skies
Best Full Art Card: Ho-Oh, Lugia,Dragonite
Worst Full Art Card: Glaceon (Bland)
Best EX Card: Kyogre 54/160 Very Colourful, Kyogre’s Profile looks good and the coral on the borders.
Worst EX Card: Most of them but Charizard because you would hope they do such a cool Pokemon justice but we get this kindergarten 3d crap
Best M EX Card: Full Art Mega Rayquaza Roaring Skies, Full Art Mega Rayquaza Ancient Origins
Worst M EX Card: Mega Lucario
Most Underrated Card: Giratina Full Art Ancient Origins (Giratina’s form and profile captured well)
Most Overrated Card: M Charizard (all of them)