Marvel ultimate alliance, Spider-Man friend of foe, Metal Slug and Nintendo Land.

I feel like I am probably forgetting something, but here goes:

1. Perfect Dark (N64) - playing the campaign in co-op mode on Perfect Agent was a blast. Having to share a very limited amount of ammo and health required a lot coordinated team work. In contrast, the more modern 1st/3rd person shooters I've played on co-op can usually be beaten fairly easily with each person haphazardly doing their own thing.
2. The Legend of Zelda: Four Swords Adventures (GCN)
3. Contra III: The Alien Wars (SNES)
4. Teenage Mutant Ninja Turtles IV: Turtles in Time (SNES)
5. Life Force (NES)


New Super Mario Bros. Wii would have made my list if it weren't for the stupid pause effect when someone dies. It is manageable with 2 players, but becomes extremely annoying with 3 or 4 players. Also, I loved Ikaruga, but haven't really spent much time playing it 2 player.

Metal Gear Solid: Peace Walker. As simple as this game is, co-op can make it so much fun, especially when doing the more complex sideops.
Resident Evil 5. I know a lot of people hate this game, but I've actually had a lot of fun with it playing co-op with a friend.

Souls series, Borderlands, most Nintendo stuff, Timesplitters, Terraria, Rayman Origins/Legends, Final Fantasy 6, Secret of Mana/Seiken Densetsu 3, House of the Dead (Wii), Serious Sam, and a bunch of others that I cannot think of right now. 

The King Of Dragons.One of the best co-op games of all history!

3D World
Dragon Quest IX
Hyrule Warriors

off the top of my head

Captain Commando (i think that this is the English name).

Have you played the Chronicles of Mystara port? Which version would you recommend?

Might try it, since I also enjoyed Golden Axe and missed this one.

If anybody's list omits Twisted Metal World Tour... you've probably not played it.

Freedom Wars, MonHun (even though I havent palyed anyother than FreedomUnite ), toukiden
Magicka 2 is pretty awesome, still playing.
Little Big Planet, always fun.
Lara Croft and the guardian of light/ the temple of osiris, these games are just wonderful.
Helldivers is also suprisingly funny.