George Broussard of 3DRealms made this post to the 3DR BBS talking about the complexity of development for Duke4Ever as compared to Duke3D a few years back. Here is what GeorgyB had to say:

Q: Saying that duke3d took longer to develop is not much of an arguement. The target systems then were 486s, it took a lot more skill to write a fast 3D (or 2.5D) game when vga wasn't a proper standard. D3D, glide and openGL do all the hard work. Even I picked up openGL in a few days, it's simple to create powerfully rendered scenes.

George's Response: Ah, but rendering isn't the issue is it? today's game are MUCH more complex. In Duke 3D all the characters were sprites. Today they are polygonal models, have to be skinned, and then animated or motion captured. A VERY long, tedious and complex process. Also games today are "deeper" and require more than key/door stuff. That means more time to develop. Note all the so-so fps games that didn't sell well in the last 2 years and you will see that they were simple compared to more complex efforts like Half Life. A game like DNF is probably 5-10 times more complex that Duke 3D was.