Genesis (Known as Mega Drive, here in Brazil) :
Sonic the Hedgehog 1-2-3, obviously.
Golden Axe (I loved to play this with my friends).
Ecco - The Tides of Time (Even if it was scary for me at the time, it was a fun game).
Captain America and the Avengers (Another good game to play with friends).
Rambo III (I was a fan of rambo at the time. Exploding choppers with a bow was fun).
World of Illusion Starring Mickey Mouse and Donald Duck.
Toejam & Earl (Crazy game! A pity they don't make games like this anymore).
Super Nintendo (Or Snes) :
Super Mario World (Like Sonic, it's a game you MUST play if you have the console).
Contra 3: The Alien Wars (Incredible hard, but a awesome game nonetheless).
Super Mario Kart (Fun race game. Even for me that I'm not a big fan of race games).
Super Bomberman 4 (Another game that I loved playing with friends).
International Superstar Soccer (I generally don't like soccer games very much. Not my cup of tea, I guess. But this one is very good!)
Metroid 3 (Samus FTW! Only bad part in the game that I remember, was having to learn how to make the Jackie Chan's jump in the walls. Arrrgh! The frustation!!!)