Mario Kart - it appeals to everybody and randomness helps more casual players as long someone isn't too good and abuses mechanics (e.g. Snaking)
Bomberman - simple and on some consoles it supports more players than usual.
Towerfall - simple mechanics, luck helps casual players.
Poy Poy - again, simple and just fun.
Virtua Tennis - everybody knows the rules and there is no need for many buttons.
Micro Machines - 8 player multilayer on 4 controllers (shared controllers) was a blast when I was young.