The point is he and his team have contributed a new engine which is now being used for at least 3 next-gen games.
He is now contributing towards Oculus Rift too which is receiving a lot of interest and praise in the industry. So much so even MS/Sony are rumoured to be interested in adding support or releasing competitors.
The pros and cons of those is not the topic of discussion.
Pretty self explanatory.
Epic also contributed a new engine, used by about 10 times that many games, CrySoft has contributed an engine, one arguably better than tech 5, Dice has contributed an engine where I would say there's no argument it's better.
and that's just the top of the iceberg, being on the management of a company who makes a new engine isn't a big deal, especially when the engine in question is a fairly bog standard mediocre engine with one revolutionary feature that didn't work. And I really wish megatexture had worked since as a 3D modeler myself,. there's nothing that annoys me more than tiled textures. but there's many tricks that mitigate or even remove the tiles that you can use.
whether he's actually contributing to rift is what is at question here. he's in management, and the only thing he's truly contributing there is his name.
What oculus needs is people who can contribute new ideas and uses. which is a much younger crowd of new and experimental developers than Carmack, they're the ones who today are who Carmack was when he was their age, some 15-20 years ago.