Gunstar Heroes, Dynamite Headdy, Alien Soldier (basically everything made by Treasure), Revenge of Shinobi, Phantasy Star IV, Super Street Fighter II (multiplat), Micromachines II (multiplat too, but comes with two extra built-in controller ports for 4 player mode).

Probably Landstalker, Castlevania Bloodlines, Contra Hard Corps, Light Crusader, Story of Thor, Mega Turrican (if you don't have an Amiga...).

Just buy Sonic's Ultimate Genesis Collection on the 360 or PS3 it pretty much has all the good 1st party games that came out on the Genesis and its a lot cheaper then buying the games separate.

If you own a PS360, you can get 50+ games on the console for $15 or less, most of them great games. If you want to play the games on the console itself, below are some of my favorites.

Dark Wizard(Sega CD attachment required.)
Castlevania Bloodlines
Phantasy Star 4(will make you wish they continued on with the series like this.)
Rocket Knight Adventures
Gunstar Heroes

First, get the 6 button controller, it will make a big difference in fighters.

Get:
The Sonic game
Phantasy star 2-4 (The 3rd one is kind of crappy but part of e series so)
Shining Force 1-2
Shining in the darkness
Rings of Power
Soleil
Beyond Oasis
Landstalker
Hellfire
Thunder Force 3-4
Gynoug
Desert Strike
Jungle Strike
Street Fighter, special championship edition
Mortal Kombat 3
Eternal Champions
Vectorman 1-2
Alien Soldier
Streets of Rage 2-3
After Burner 2
Castlevania Bloodlines
Devil Crash
Earthworm Jim
Gunstar Heroes
Dynamite Headdy
Castle of Illusion
Quackshot
Ranger-X
Road Rash 3
Sparkster
The Hyperstone Heist

Yeah, they definetely lost their way after PS4, the way the story of Dark Force was building up, could have beenan awesome 3D singleplayer experience.

This is the correct answer.

Gunstar Heroes, Streets of Rage 2, Probotector/Contra Hard Corps, Zombies Ate Mt Neighbours, Street Fighter II Turbo: Hyper Fighting, Ghouls 'n Ghosts, Golden Axe 1+2, Earthworm Jim, Columns, Castle of Illusion, World of Illusion, Quackshot Starring Donald Duck, Marko's Magic Football.

All of above (I've played) are decent games.

Do you know if there are any notable differences between the SNES and Genesis version of Earthworm Jim?

Not sure mate. I've only owned the Megadrive version (Genesis) so..

Saying that, I wouldn't think there would be much difference between them -  well, apart from improved graphics on the SNES. But yeah, look it up on Youtube.. I'm sure there would be a comparison on there, or something.

Captain America and the Avengers