From what I understand, gpu's are at a bottleneck kind of and will not be making any huge leaps until they reduce their die sizes. And from the accounts I have seen, nVidia is going to milk as many generations as they can before shrinking dies. All of which is to say we are probably a few years from any drastic leap forward as far as gpus. You can see this in how small of a performance increase there was between the 7xx series and 9xx series cards.
Xer0 mentions the titan, 980Ti, and Fury, but those are enthusiast cards in the $700+ category. If that is your price bracket, then currently, it looks like the 980Ti is the most performance per dollar efficient model.
However, the geforce 970 is an excellent card and overall the most economic as far as current gen performance per dollar. Its the best option unless you have money to burn.
Xer0 pointed out controversy about the memory. Well, long story short, the card was/is marketed as a 4gig card. And it does have 4 gigs of vram, but the rest of the architecture cannot use all 4 gigs and it tops out at around 3.5 gig. This ignited a lot of anger over false advertising. However, it looks like that missing 500mb does very little in terms of reducing performance. Its very rare that games are bottlenecking on vram.
All that aside, the 970 is still a very good card, especially if you get a non-reference one.
Also, it gives you the option of buying a 2nd one down the line and running SLI. And 2 970's in SLI approach titan x levels of performance for a much lower price.
