The Orange Box is great you will enjoy that tons, CoD4 too but you might be slightly dissapointed by Gears of War.
Anyways, I'm playing through Crysis, already beat it on hard but now I'm giving Delta a go and trying to see what new routes I can discover in levels, aside from that I've really been enjoying playing through Portal, the puzzles get old but GLaDOS is such a great character and it really enhances the game, plus 3rd party maps are also fun to play.
I was replaying Bioshock but completed the Fort Frolic level and lost interest (since pretty much everything after that is not as good in my opinion if you already know the plot twists).
On the DS I've been playing Phoenix Wright Ace Attorney and just finished the 4th case... the game is awesome, the quality of writing is just excellent and everything is done right from the way graphics and music cues are used to the testimonies and the situations and the way every case is much more than it tells at the start.
My next games might be Viva Pinata (PC) or Unreal Tournament 3 though Sins of the Solar Empire looks great as well... maybe I'll just get Phoenix Wright Justice For All for my DS