sod Elite.... Frontier!!
MegaLoMania - definately a great choice. (though shame you didnt google -that- spelling Zetr0!
as for the dungeon crawlers... well this is one of many reasons why Bloodwych is king of RPGs!
Rainbow Islands - the other two in the trilogy managed it, shame this one wasnt simultaneous. [edit - damn you KG - i thought it first!]
IK+ should be 3 player too, and Indy Heat 4 player.
Sim Ant - linkup black vs red ant play!