I had the same problem too with my games, especially the latest game titles untill I upgraded my graphic card. Currently am using the ATI Radeon™ HD 4600 Series. Smooth all the way with no lag.
I too have had some game lag, however I know with scaling back and using lower settings I can get by.
I had an NVidia card, but have since upgraded. I do believe I had an other type of card put in, and with it I can do any game.