Playable with one regular joy + buttons per player:
Two Tigers
Tetris
Altered Beast
Golden Axe
Mario Bros (not Super) - everybody forgets this one, it seems like.
Xybots (used special joysticks, but can be played fine with a regular joy + two rotation buttons)
Rampage (up to 3 players)
Silk Worm
...
Also try these, if you've got the controls:
Blasteroids, Pong (dual spinners)
House of the Dead, & all the lightgun games
Ikari Warriors, Time Soldiers, Heavy Barrel, etc. (rotary joysticks)
Cabal (dual trackballs)
Atari Football / X's & O's (dual trackballs)
Marble Madness (dual trackballs)
Can't agree enough about Smash TV, you can play that for hours. If you've got the 4-stick setup for it, download Mutant Storm, too. It's a PC game, not MAME, but it's a two-stick shooter like Smash TV, that plays well on a cab. 2-player Karate Champ is cool, too, but you're supposed to have 4-ways for it, so avoid the diagonals if you're using 8-ways.