Stalker is an rpg, JC2 is horrible optimized for the computer, and ARMA 2 is for people who have a computer from the next century. That's why you can't run it on max settings.
Why does the genre matter? Also, you got all of those wrong.
STALKER is not an RPG. Perhaps if you consider detailed weapon stats and customization with a few player stats changed only by a few objects an RPG then sure, but it's really not an RPG at all. The reason I can't max it is it's a DX11 and the GTX260 is a DX10 graphics card. If you turn DX11 off and revert it to 10 it runs fine.
JC2 is one of the better optimized games I've played. I've had some 60-to-30 framerate drops, but if I turn off Fraps I honestly never notice any disruptions severe enough to interrupt play.
ARMA 2 is optimized like stuff. The fact that a game can look like this:
and run at barely playable framerates that fluctuate severely depending on the complexity of the scene is proof that it's poorly optimized.
The surest proof that a game is optimized terribly is if you can't get a consistent framerate while playing.
Poll