GTX 670 or GTX 760? Which is better for gaming?

Well 670 has overall better scores in all kinds of benchmarks. More CUDA cores as well, just as an example. However the 760 being a generation younger and having GPU Boost 2.0 it could be great fun overclocking it, also it has OpenGL 4.3 - but I don't suppose that matters to you . Though if you are not exactly a OC maniac I would go for the 670 - I know it is weird to go for an older one, but it will score higher FPS if thats what you are looking for.

EDIT: I also agree with Traciatim - spending just a little more would be worth the 1 generation :) if you can spend that kind of cash :)