I will be completely honest, I’ve never looked a lot at the artist names of cards, unless there are some very similar ones in a single set; so when it’s obvious they are made by the same artist.
But since this topic has been brought up (great posts btw @pokesoap ! Both of them), I will of course join in.
So, I’ve looked at some of my favorite cards regarding artwork, and then looked at some other cards these artists made:
Let’s start with my favorite Pokémon artwork of all time:
And I can quote my post in @charchu 's give-away with the reason why (it’s just amazing!! 
):
Some other great artworks from this same artist:
The calmed yet serenity way the Pokémon have been drawn is amazing. All of them are majestic, fearsome or cute in their own way, and a lot of them (like in the examples above) look like they’re having a great time. Certainly an amazing artist.
Then my second favorite artwork, and my favorite Pikachu artwork:
It looks so happy, and the waterfall and tree in the background is really want makes this card, which is also why I like it so much.
Some other great artworks from this same artist (I just realize he’s also responsible for my favorite Pikachu Jumbo. And he’s also responsible for the Pikachu Outbreaks, all Poncho-wearing Pikachus, and a bunch of other Pikachus):
And some other examples:
The majority of the artworks I really like are made by Kouki.
**Sanosuke Sakuma:**Sanosuke has a lot of colorful artworks. What I also like about them, is that they usually tell a story or scene. Here are some great examples:
Oh, and I also really like this artwork, but I have no idea who the artist is (since it’s covered…):
As for an artist that isn’t really my kind of style:
Every artwork is a Pokémon made out of clay. First of all I want to say that they are very well done, and I can definitely give the artist credit for that! But personally I prefer drawn or even CGI Pokémon over these clay figures. Here are some examples:
This is a bit of a weird one… The artwork-style of this artist are all over the place… 
Personally I’m really not a fan of these kind of drawn Pokémon with thick lines, and unrealistic artworks; the kind of artworks that actually look drawn, instead of a photo of the Pokémon in their natural habitat:
But this same artist also has some pretty good artworks like these:
And also some artworks that are kinda in between:
Almost as if this single artist are actually three different persons. Pretty weird. Oh, and I personally prefer the second style out of the three for sure.
@smpratte I guess you’ll add a nice story about Kouichi Ooyama’s artworks, Scott? 
Greetz,
Quuador