Newer Kabuto (HGSS). It's supposed to look cute (at least I think it's cute) and mysterious, not like a freaking Metroid that's going to eat you.
EDIT: Oh look, 300 posts.
I didn't like Pikachu's Red/Blue sprite
Jigglypuff's sprite is fine in the first game, but it's HG/SS sprite is...not jigglypuff.
Fair enough, some of the Generation I sprites are horrible, but bear in mind that the games were made long before the anime, people who are asuming that the fact they don't look like they do now was a mistake, it wasn't
No not at all. Look at the original artwork. The sprites from Red and Green look nothing like the artwork. The Anime got it right.
Pikachu was chubby back in the mid-90s, but has gotten skinnier over the years in the official artwork, and this has been reflected in both the games and TV show:
Porygon says "Hello".
Obviously there are some exceptions. It would have been really bad if they screwed up Porygon.