I'd recommend all the games you've listed.
COD4 MW is a great game with great storyline and gameplay.
COD6 MW2 is also requally good, but with a short single player campaign.
Crysis with it's outstanding graphics and gameplay.
Crysis 2 with good visuals and gameplay.
Metro 2033 with a dark atmosphere and a great storyline.
Basically, they're lots more.