Ive got to say that the SNES, N64, Sega Genesis, and Sega Dreamcast share equal parts of nostalgia for me.
SNES
Kirby's Dreamland - Extremely cute and fun to play. I played the hell out of the DS version when it came out.
Earthworm Jim - just because it was so weird that someone like me HAS to love it!
Donkey Kong Country - My favorite sidescroller (That isn't a Sonic game

)
N64:
Goeman: Mystical Ninja - I just fell in love with the artwork and gameplay

Banjo Kazooie/Tooie - Same as Goeman, but include great BGMs

Legend of Zelda: Ocarina of Time - Just cause its OCARINA OF TIME! (Though I also got hooked on Twilight Princess)
Megaman 64 - I just liked its style.
Mario 64 - The N64 version was more fun than the DS version and always will be.
Genesis:
Shining Force - since it was the only game I played on it, but still, it's my most favorite turnbased strategy RPG
Dreamcast:
Sonic Adventure 2 and all the reduxs of it - Best 3D Sonic game ever.

Powerstone and Powerstone 2 - Sega's Super Smash Bros. I remember playing this with my INTP friend all the time. Yum.
Evolution 1-2 - I just loved this game.

Grandia 2 - A kickass classic that should be played if you're into RPGs
Oratario Tangram : Mainly for the giant robot fighting fun
I need to get me some ROMs when I get back to the States...