With FPS-style combat and a nice backstory, Vendetta is worth checking out, but don't expect anything special.

In case you haven’t heard of it, Vendetta Online is a space-based MMORPG. The manual is dominated by a long (and actually decent!) timeline-style backstory. In ways it resembles the story behind Total Annihilation. Humanity finally colonises space, factions squabble over cybernetic enhancements, hilarity ensues. Well maybe not so much hilarity as bloodshed. Either way, it sets the game up nicely for some action.