Ecco! right on msleeper. My favorite game on the genesis, next to sonic.
Oregon trail.... fantastic. Computer class in elementary school = oregon trail.
Anybody play Kyrandia? I remember liking that game. It was a point and click fantasy type of game. Much like the later Kings Quests, which I realize most of you didn't like.
I also had fun with the Dr. Brain series, but the puzzles are probably too easy now that I'm not 10.
NES: Obviously zelda, double dragon... and I think one of my favorites was The Guardian Legend, which was a walk around and shoot things typea game, with "levels" where you turned into a plane and played a top-scrolling flying shooter.
SNES: Bomberman (also on nes, and other places... I played it on SNES), Tetris Attack