I don't particularly like these as coop games as such but your milage may vary. The New Super Mario Bros game on Wii is tolerable as a two player game without descending into utter chaos, and Super Mario 3D World is good as a two player game too.
I'd also second Rayman Legends, and even though you said you didn't particularly like the genre, Castle Crashers is a fun one, and by the same developers, Battleblock Theatre is a goofy coop puzzle platformer with a lot of charm though it does get hard as balls later.
Another one I thought of: Toejam & Earl in Panic on Funkotron for Sega Genesis
A lot of folks don‘t like it but I always had a good time playing it. It’s kind of a simple straightforward platformer but I like the cartoony aesthetics, funky soundtrack, and think it's fun enough to be worth playing, especially in 2-player mode.
I like it more than the original TJ&E which I think is too slow paced for my liking. But my opinion is definitely in the minority with that and I'm very possibly blinded by nostalgia!
SNES: Kirby Super Star for the SNES. It is also for the Wii in the 20th anniversary collection, and there’s an Ultra version on the DS. I think it’s my favorite co-op game of all time…
Later on in life, I’d try Goof Troop, it’s like a co-op puzzle game, nothing really is like it.
And also Super Bomberman 2. When we played, we just co-oped through each of the 10 stages in the Battle Mode!
Genesis: Yup, Streets of Rage. I also have fond memories of Sunset Riders on the Genesis! Also NBA Hangtime, NBA Hangtime for Genesis or 64 is pretty good, I never played the SNES version. NBA Jam might be okay too but for control and music, I prefer Hangtime. You can even create a player! My character always had the basketball head.
@andrewelmore As a dad of two boys, one almost five and the other two and a half, they are really interested in seeing what kinds of games are out there having seen me play a lot! The younger doesn‘t really do anything but push buttons but the elder one is really trying hard to play games and is doing pretty good so far!
I found that good old arcade games seem to work best =) They usually don’t have many buttons, are quite action packed to keep them interested and have a good time limit so they don‘t get bored quick.
My eldest and I played Final Fight a lot, just to give him practice on using buttons while I moved the character, then switching over so he could move them while I attacked. We’re gonna try more over the summer, but so far I've found it a great way to start him on the long road to video games as a whole.
