didnt own a ps1 until after my n64, so my views are a little biased towards nintendo. ive owned a ps2 for some time, but never feel "comfortable" playing it, if that makes any sense.
favorite current gen games on ps2:
GTA series
Final Fantasy X and XII
mgs2 and mgs3 are excellent games
dance dance revolution max. the first DDRMAX is 10x better than DDRMAX2
gamecube:
smash bros. melee
animal crossing
resident evil 1 and 4
if you must get a THPS game get tony hawk's underground (tony hawk games are fun but repetitive and i only like to play them on the cube)

viewtiful joe
paper mario: thousand year door
BUT if you can get the first one on N64 it blows this one out of the water, and super mario RPG on SNES beats them both
combined
final fantasy crystal chronicles always sparked my interest, but to play you need a GBA and a GC/GBA connecter for
each player.
xbox:
halo 1 and 2 ofcourse
fable
spider-man 2 is fun until the novelty wears off
xmen legends