They are different though. Open expansive world vs a linear storyline that is heavily voice acted by well know VA's. Fallout is unique in that anybody can be anybody. As for story telling it would be quite difficult to make up your own story in GoW universe fit for TV.
It's one reason why Halo show sucked. It wasn't the Master Chief.
I'm not arguing with you (I don't even know your opinion lol) but merely pointing out why I think it'll flop. But I could be proven wrong in the end.