Capcom Vs SNK 2 and GGX2 are probably the most perfect games ever made.

Pros for CVS2:

Tons of characters
Team play
Make your own fighting style
Voice Overs for the characters were nice to listen to
Perfect controls
Chun-Li and Mai, the two best video game sex goddesses

Pros for GGX2

Best storyline any video game (just the sheer amount of stuff that happens in the game's story was awesome)
The characters personalites and their backgrounds rival that of some RPG characters
Best soundtrack any video game can ever hope of having
I-No and her sexiness
Johnny's moves and attacks just plain rock
The animations and sprites are the best spritework any video game has ever seen