Here are ones that I've had a lot of muilt-iplayer fun with in the past:
Dungeons and Dragons Tower of Doom (3 player / arcade, PS3)
Gauntlet (4-player / arcade, Genesis)
Dungeon Explorer (5-player / TurboGrafx)
Donkey Konga (4-player / Gamecube)
Hansha de Spark 4-player / Saturn)
Three Dirty Dwarves (3-player / Saturn)

games I'd like to try multi-player but never had the chance:
VATLVA (6-player / Saturn)
Car Battler Joe (4-player / GBA)
Shining Soul II (4-player / GBA)
Gurulogi Champ (4-player / GBA)
Kuru Kururin Paradise (4-player / GBA)
Kururuin Squash (4-player / Gamecube)
Billy Hatcher and the Giant Egg (4-player / Gamecube)
Ghost Squad (4-player / Wii)
Ivy the Kiwi (4-player / Wii)
Let's Tap (4-player / Wii)
Revival Chase (4-player / PCE-CD)
Champion Wrestler (4-player / Playstation JPN)
Micro Maniacs Racing (8-player / Playstation)
Speed Punks (4-player / Playstation)
Sega Ages 2500 Series Vol. 21: Quartet (3-player / PS2 JPN)
Drive to Survive {The Gaidou! Genocide Grand Prix} (4-player / PS2)
Giga Wing 2 (4-player / Dreamcast)
Outrigger (4-player / Dreamcast)
American Battle Dome (4-player / SFC) [janky but probably fun]
Spark World (4-player / SFC)
Ketsui: Death Label (has an 8-player mode?! / DS)
Snoopy vs The Red Baron (6-player? / PSP)