John Carmack slaved away writing super optimized ground breaking realtime 3d game engine code that created a multibillion dollar industry.

Adrian Carmack mostly took photographs of clay scultures (and in some cases actual plastic toys, in the case of the chainsaw and pistol used in the original Doom), and digitized them in Corel. Something any half-way decent art student could do (not to discount the iconic visual style of Commander Keen and Doom!)

It was Adrian who walked away with 41% of the >100 million dollars company!

Which just goes to show that technical chops and business chops are entirely unrelated. I think John Carmack did alright anyway.