3 years ago, say 2013. Lets Google and look what we have.
> http://www.gamesht.com/2013/04/03/top-5-best-nvidia-graphics-cards-for-gaming-in-2013/
Lets take the GTX 660 for around 300 USD, which performed less and was cheaper in price compared to todays GTX 970. Thats because i coulnd't find a 670 benchmarks comparison. Here some comparison, with 1080p and mostly ultra or high settings. Offcourse the 970 is better. My point is, that 3 years old cards are still good for gaming, with lower quality settings and at least 30 fps.
The Witcher 3, 1,920 x 1,080, graphics: medium, post-proc: high (AA, SSAO)
GTX 660: 32
GTX 970: 77
>
http://www.techspot.com/review/1006-the-witcher-3-benchmarks/page2.html
Battlefield 4, 1,920 x 1,080, DirectX 11, 'Ultra' Settings
GTX 660: 37
GTX 970: 78
>
http://www.bit-tech.net/hardware/graphics/2014/09/19/nvidia-geforce-gtx-970-review/6
The Elder Scrolls V: Skyrim, 1,920 x 1,080, 8x AA, 16x AF, 'Ultra' Settings, w/ High Res Texture Packs
GTX 660: 79
GTX 970: 152
>
http://www.bit-tech.net/hardware/graphics/2014/09/19/nvidia-geforce-gtx-970-review/9
Ahh, here I found a GTX 670 comparison.
Battlefield 4, 2560*1440p (!), Ultra settings, 2xMSAA
GTX 670: 37
GTX 970: 62
>
http://www.guru3d.com/articles_pages/gigabyte_geforce_gtx_970_g1_gaming_review,15.html