What are the best offline co-op games?

[azure]

If you like Musou style games, those are a blast with local co-op.

[telly]

While I haven't done this myself, I heard Resident Evil 5 is way better with a co-op partner, since the AI is kinda crap.  I still enjoy the game solo, but I certainly could imagine that game being a lot more fun with a competent player partner.

I've played it a little bit with my roommate, and it is a lot of fun co-op, while still being a decent challenge.

[bikingjahuty]

A few really god ones I've played:

Champions of Norrath and Champtions of Norrath Return to Arms
Yoshi's Wooly World

[brazbit]

* Bubble Bobble
* Contra
* Rampage (It can be co-op... until one of you "accidentally" eats the other and then it becomes a brawler forget the stinking buildings... meanwhile the third player knocks down the rest of the city taking the lead and the newspaper pops up reminding you what the whole point is and then it is co-op again until that damned monkey boy knocks you off a building....)
* Double Dragon (At least until the end)
* Gauntlet (Blue wizard needs food badly... ahh foo... ^%@^#!! the damn elf just shot the food... and thus begins a life long hatred of elves.)
* Golden Axe (All's fair in love and gnome punting)
* TMNT/Xmen/Simpsons etc... cooperative brawlers (Up to six people crowded around a single cabinet working together is awesome)
* Xenophobe (Triple Split Screen action)

Being a huge Atari fan I wanted to put more Atari games on this list but multiplayer games were almost exclusively competitive or turn based back then. Almost all of these became series for good reasons.

[dreama1]

* Bubble Bobble
* Contra
* Rampage (It can be co-op... until one of you "accidentally" eats the other and then it becomes a brawler forget the stinking buildings... meanwhile the third player knocks down the rest of the city taking the lead and the newspaper pops up reminding you what the whole point is and then it is co-op again until that damned monkey boy knocks you off a building....)
* Double Dragon (At least until the end)
* Gauntlet (Blue wizard needs food badly... ahh foo... ^%@^#!! the damn elf just shot the food... and thus begins a life long hatred of elves.)
* Golden Axe (All's fair in love and gnome punting)
* TMNT/Xmen/Simpsons etc... cooperative brawlers (Up to six people crowded around a single cabinet working together is awesome)
* Xenophobe (Triple Split Screen action)

Being a huge Atari fan I wanted to put more Atari games on this list but multiplayer games were almost exclusively competitive or turn based back then. Almost all of these became series for good reasons.

pacpix managed to list a couple to my surprise.

[kashell]

Final Fantasy VI can be two player, even though it's not very involved. You take control of a some folks in battle and your friend takes control of the rest. It doesn't sound fun, but back in the day my friend and I would just bond as we power leveled by killing Cactuars in that tiny desert. It was a lots of fun.

[ignition365]

I've quite enjoyed playing Demon's Souls swapping back and forth every time you die.

[turf]

* Bubble Bobble
* Contra
* Rampage (It can be co-op... until one of you "accidentally" eats the other and then it becomes a brawler forget the stinking buildings... meanwhile the third player knocks down the rest of the city taking the lead and the newspaper pops up reminding you what the whole point is and then it is co-op again until that damned monkey boy knocks you off a building....)
* Double Dragon (At least until the end)
* Gauntlet (Blue wizard needs food badly... ahh foo... ^%@^#!! the damn elf just shot the food... and thus begins a life long hatred of elves.)
* Golden Axe (All's fair in love and gnome punting)
* TMNT/Xmen/Simpsons etc... cooperative brawlers (Up to six people crowded around a single cabinet working together is awesome)
* Xenophobe (Triple Split Screen action)

These are great answers.  I like the cut of your jib. 

[rayne315]

anything lego is always fun playing with people