This came up in a smpratte Q&A and I thought it was really interesting.
It was something to the effect of:
1 - What’s a card you didn’t care for but has grown on you over the years.
An additional question
2 - What’s a card that you were crazy about that you now don’t have much interest for.
When I started collecting in 2000 and the Japanese Pokemon released the VS & e Series. I really didn’t have a liking to the new design style. Boy was I wrong! 20+ years later I can’t get enough of them.
Essentially the entirety of e-Series and the EX era
Poké Dude promo, it’s so bizarre like Imakuni?
Base set Charizard, so over-hyped, annoying to look at in prices and overall meh.
As mentioned already pretty much the entire e-Series cards. I don’t think there’s too many cards I didn’t care for back in the day that grew on me, as I pretty much liked most of them anyways. However two cards that come to mind are Neo Genesis Slowking and Fossil Lapras I think. Now vice versa though, there’s quite a few cards I absolutely would’ve died to have as a kid, that I just don’t care too much about nowadays. Pretty much the entire Neo Destiny set to be honest. Probably very surprising as it is considered maybe even the best WOTC set period by a lot of people. Dark Tyranitar, Dark Feraligatr, Dark Gengar, Dark Ampharos for example I all loved dearly not too long ago even. But when I actually think about these cards… I don’t know. They look way to “modern” in a way for me if that make’s sense. Surprisingly also not a huge fan of most of the Shinings for some reason. Apart from Kabutops and Celebi I’d all rank them a solid 7/10 ok-ish. Cool but nothing I absolutely have to have. Another one that comes to mind is the Dark Dragonite. Still absolutely adoring the Fossil one, but my love for the Dark one has dwindled immensely.
Shadowless Charizard. I’m not much of a Charizard guy and think he’s way too popular compared to other Pokémon (especially Blastoise, Venusaur, and Mewtwo tbh). For years while its value increased I didn’t care too much for it. After pulling the same Charizard artwork from the Japanese and Korean CP6 boxes I was content with it, since it is a good artwork.
Only very recently the Shadowless version has grown on me, even though I’ve already seen it tens of thousands of times before in the past 6.5 years I’m collecting. A few months after the shiny Charizard V from Champion’s Path was released, which I liked instantly, I decided to buy my top three favorite Charizard cards: English Shadowless Base Set; English Champion’s Path shiny Charizard V; and Japanese 276/XY-P Charizard promo (the artwork where he’s being attacked by Venusaur). Currently waiting for the last one to arrive. Kinda wished I had bought these years ago considering their prices now, but figured better late than never, especially now that I can still afford them… 
Mimikyu in general. Some newer members might not know, but I didn’t just collected Pikachu and Seviper in all languages, but Mimikyu as well. When I first saw it in the anime I liked it a lot, and started a collection for it almost instantly.
Later when the Team Up set released (which contained four Ultra/Secret Rare Pikachu cards - times 11 languages; four Ultra/Secret Rare Mimikyu cards + two more regular Mimikyu cards - times 11 languages; and ten English Full Art Supporter cards), I decided to stop my Mimikyu collection for financial reasons. Not too long after I stopped, I also realized I hadn’t looked close at some of its artworks even though I was collecting it, unlike my Pikachu, FA Supporter, and Moltres collections, which I looked at (and still look at) quite often. So stopping my Mimikyu collection was definitely the right decision. Here it is in its current/final state for anyone wondering (with a lot of gaps near the end). I don’t even have any of the three newer Mimikyu artworks.
Greetz,
Quuador
Delta Species holos and ex have grown on me. I used to dislike the ex as I was used to sparkly silver cosmos holo borders and thought the delta style didn’t differentiate enough from the regular holo. Now I appreciate their change in style. Call of Legends Secret rares have also grown on me. At the time I remember thinking the set was terrible and the cards were unplayable = worthless.
I agree, particularly on VS. At the time scans were quite rare but spoilers with english translations of the cards were around. And for playing the game, VS sucks - big style! But the artwork is cool.
I’m now finding I want to collect anything VS. I guess it’s emotional retribution for not liking this set back in 2001 and just thinking, na I’ll just skip this one and move to the next set, which by the way, never happened. 
Japanese cards in general.
I went from thinking “lol I’ll never buy Japanese cards” to actually preferring them over English.
Skyridge Gyarados. Never cared for it and now I really respect Skyridge set for it’s low print run and the art looks amazing!
I remember seeing the e-series in stores as a kid and thinking Pokémon jumped the shark, but now they’re some of my favorites.
cards in Japanese have grown on me, esp the old back stuff but also up through ~2014 or so. The clarity of the holo patterns they use is just blindingly nice. This doesn’t mean I’ve cooled on english though and I’m still primarily an english collector.
2004-2007 EX era reverse holos with the set stamp have also grown on me. I used to hate stamp covering up the art but I have come to really appreciate the variant.
DP, HGSS and BW era cards are growing on me as well. I was exclusively a WOTC-EX era collector up until relatively recently. No real justification for that, I think it just takes time to digest all the cards that are out there.
Can’t think of any cards I’ve cooled on. I have never really been high on pre-neo WOTC but my interest hasn’t exactly gone down either.
Pokemon has a lot to offer. there is a lot of opportunity to get excited about stuff you previously overlooked 
E-series (skyridge, aquapolis, expedition, VS) and neo series cards. Honestly, charizard is once a card that I was nuts about, but after collecting a bunch of them, I’m over it. Not super interesting art overall,although the secret rare EX era charizard and neo dark charizard are great.
E-reader cards grew on me quite a bit, like everyone else. At first I hated the border… now they feel special and bold, and the art is some of my favorite. They also feel great to hold: something about the border and metal inlay makes them feel extra valuable.
Team Rocket set was the first set that departed normal Pokémon when I was a kid. I pulled a Dark Charizard, and remember feeling like I was kind of excited to have a Charizard, but also felt like it was the first Charizard that no one cared about. Since then, the set’s become one of my favorites.
Also: Base set Machamp holo. It’s honestly one of my favorites now, lol – the pattern of Machamp’s fast-moving arms plus the holo pattern and coloring… it’s instant nostalgia for me.
I’ve also come to appreciate full art modern cards, depending on how they’re executed / the artist. Honestly, scream promos probably pushed me there.
Definitely have cooled off on Mimikyu:
Same thing happened to me. When I came back to Pokémon in 2018, Mimikyu was one of the first “new” Pokémon (honestly, meaning anything after Gen 2… hardly new) that I gravitated toward. Many of the others didn’t interest me, but I liked the story and creativity behind Mimikyu.
I went ham on it and at some point I realized I didn’t really care for the cards much – also as I realized holos didn’t mean the same thing as they used to. And then realized it became a “fan favorite,” but kinda felt propped up in a way by TPCI. The timing was great, because when I was ramping up on Pokémon was also when the Scream cards came out – and Mimikyu was by far my favorite. After time, the Pikachu and Psyduck click the most with me.
I’m sensing a trend in this thread thus far.
Sorry to shill my own thread but on the topic of e-series border, this whole experience with E-reader archive group HitSave! made me enjoy e-reader cards 100x more, it really is cool when you think about it that every E-reader card has a built in hidden story.
www.elitefourum.com/t/archiving-the-2002-e-reader-trophy-cards-no-2-boy-added/32246/1
Delta species cards grew on me, they were what was new when I first started collecting as a kid at the time I saw them as just being incorrect and was confused as to why they would exist, I remember other kids thinking they were fake because we knew those pokemon weren’t those types. Now I see it as an interesting gimmick that mixed things up in a way we haven’t seen since.
As for what I like less that would have to go to the energy designs that started in ex emerald “Matrix energies” the issue I have with them is solely based on playing with them, in play an energy is mostly conceal being tucked under the pokemon it’s attached to, with every other energy design this isn’t an issue as the corresponding colour fills the card so you can still tell what type of energy is attached. but matrix energies have a black background, I’ve seen so many people who use matrix energies because they think they look cool constantly pull the energy out from underneath the pokemon to check what type was attached. Yes the design looks cool but it impedes the use of the card in play.
I agree.
HGSS era. I remember not caring too much about the era but it’s honestly starting to grow on me recently! It was such a short period of time and only a few sets have the border design and all that. There are cards that I’ve always loved such as HGSS Ninetales holo, but recently I’ve started to like all of the cards more and I really regret letting go of most of my HGSS bulk. I don’t have much of it left. Really sucks 