In games, yes, Maxwell is very efficient. Compute power draw is totally different.
4.6 TFLOPs GTX980 gets WITHOUT clock and power draw cap. Non-Reference cards for example while processing OpenCL can draw 277W which Tom's Hardware in their review have proven. If we have clock cap, and power draw with reference Bios in OpenCL you get 185W of power draw, but TFLOPs performance drops dramatically.
GPU is as it states: General Purpose Unit. If we will judge architectures by the way they can handle games we are getting to ridicoulus assumptions.