I like decent simulation games. Unfortunatly many games nowadays have "Simulation" in their title but are far from being simulaton (poor reality). If I would have to name a few games I would say "King of the Road" aka. "HardTruck 2" for trucking simulation, "Live for Speed" for racing simulation, and "Flight Unlimited 3" for flying simulation.
I also like strategy games a lot. (Warcraft series, Settlers series, Sim City series, City XL, Outpost 2, etc.)
I do like squad based tactical games especialy SciFi themed (X-Com seires, UFO Extraterestial, UFO Alien Invasion - still in development).

Anywhay in games I value good gameplay (smoth controls, decent lenght, good replayability) over the state of the art graphics. Unfortunatly there are many games where developers spent a long time making superb graphics and in the end forget about the gameplay. Also if we talk about simulation games I demand for them to be as realistic as posible.