Games you'll definitely re-play ?

There are some games that are too good to be played only once or twice, games that should be re-played over and over just to be reminded of how awesome they are.
I will definitely play these again:
-Portal 1&2
-Darksiders 1&2
-Metro Franchise
-Call Of Duty: Modern Warfare
-Call Of Duty: Black Ops
-Mass Effect Franchise
-Bulletstorm
-Crysis Franchise
-Dishonored
-Prey
-Fallout 3
-Assassin's Creed II and Brotherhood
I may have forgotten some titles, though.
What are the games you'll sure play again ?