Geforce 650 Ti baddly displays shadows

Hello dear Community,
I have been having problems with my graphics card, EVGA Geforce GTX 650 Ti 1gb. The problem is that the shadows in some games (LoL and Battle for Graxia) have a "pixeleated" display. This problem also occurs with Darksiders, but this time I see pixels on everything that is about 10 in-game meters in front of War.
I am pretty sure it is a problem with the game or my drivers, because a friend with a lower end GPU doesn't have this problem. What should I do?