Well at some point although to many this measures seem a little extreme think about the money... the sum when it comes to these kind of things is enormous
I played and liked both Bioshock games.
The feeling in those games were grate and those battles with Big Daddy were very fun (you will know what i mean after playing the game).
Start with the 1st one to have an idea over the story.
Starcraft II would be my recommendation if you PC is up to the task. Also the battles on Bnet are pretty fun and there is a big community waiting for players to join.
What i like about this game is that although it appears every and every year with a new "version" the game still remains awesome.
This is the year i managed to get an official copy and played a little on internet and all i can say: OMG the game is good.
Keep up the good work devs