I'd recommend:
APB: Reloaded, it's a free MMO online game similar to GTA. Furthermore, All Points Bulletin is a multiplayer online video game for Microsoft Windows developed by Realtime Worlds and was acquired by Reloaded Productions, ...
Planet Side 2... is a Massively Multiplayer first person shooter that delivers truly epic, massive combat on a scale never before seen in stunning, breathtaking detail.
If you don't mind RTS you could give DOTA 2 a try. You'd need a beta invite which isn't hard to come by these days.