A 660 OC will allow you to play almost everything on ultra settings. I play Far Cry 3 and all of the Crysis games on my 660 OC maxed out with no problems. Now, I don't get above 60fps in crysis 3 or farcry 3 maxed out on the settings, but I never drop below 35fps even in the most demanding scenes.
So is the 760 worth the extra $60, depends. In the future it might give you an extra year before needing to upgrade since it is newer. But then you could always just SLI 2 660 cards and only spend $100 more than you would on a single 760.