Oooh let me think...
Pokémon is the big one of my childhood, Blue in particular, and Squirtle as my first Pokémon. From that pretty much stems everything Nintendo-wise, I got a N64 for Pokémon Stadium, played a few other Nintendo games, wasn't much of a giant fan, but then I saw Pikachu was in this new "Super Smash Bros. Melee" game, got a Gamecube for it, and that began my love for Nintendo pretty much.
Outside of that though I usually played my Mega Drive (Genesis) as a kid, and I fondly remember Sonic the Hedgehog, Toejam and Earl, Ecco...
Oh and the game that pretty much got me interested in the English language as a whole (as in Literature and the like) was Final Fantasy VII.
Yep, I played the game with terrorists, swearing and cross dressing when I was a little kid. Funnily enough I didn't complete it until last year, heh.
So yeah the big three are probably... Sonic Jam (it was a compilation of the first 3 on the Sega Saturn and it was brilliant), Pokémon Blue and Final Fantasy VII.