Yes, even though the 4850 is kind of old by tech standards, it's still a very decent card.
And compared to the x1300 it's no question you will see a major improvement. (According to Tom's Hardware graphic card charts, the 4850 gives about 6.5x the performance of the x1300, so I think you'll notice!) Only with the release of Skyrim and BF3 am I now thinking of upgrading my 4850.
I've been able to play most games at good graphic levels up until now. Admittedly I have not played all of the newest titles. I'm not real familiar with the graphic demands of Dead Island but my brother has been playing it at 1680x1050 and has had no complaints of graphics. I played black ops on my 1080p display without any issue. I don't know what FPS I was getting but I'm extremely sensitive to low FPS (they hurt my eyes) and I didn't have any problems playing the game.