[Derpdiherp]

It's really going to depend on what you're doing with the graphics. As soon as you start emulating basic shaders for effects on the CPU by comparing and writing to a screens worth of pixels you'll see where the bottleneck ends up.

On the other hand if you're wanting to make something with the graphical complication of Mario or Mega Man ( purely sprites - no effects - lighting and other things maybe done with alpha blending ) then you might find it makes sense to stick to working with the CPU.