Mass Effect trilogy (play them in order).
I would also suggest Fallout 3 (i've only played the regular one, not the expansions like New Vegas).
I've heard the X-Com games are good, but haven't played them yet.
Luke Kuechly Collector
pending: w8lifter28 (custom),
Don't ask me how much I want to offer. Come with a price in mind. If I don't want it or think it's worth that, I will let you know.