Well recently me and @TheRandomness made a '2006' PC, and in it we installed two 8800GTXs, which despite their performance back then struggled to really do anything more than play games from the era notably Oblivion (which running in my system on a single 8800 got around 70 to 80 fps at max settings, a far cry from my 'low end' GTX750ti which gets an average 150 to 250fps during gameplay. This shows that the current GPU architectures perform better each generation by a large amount, maybe only the best of the best GPU of the last generations can compete with a respectable GPU before only competing with 'budget' gpus e.g the GTX 680 Vs say a GTX970 or R9 380.