The Witcher was pretty fucking epic, that's true.
I wanna see an Elder Scrolls movie.
But we have to remember that films based on already hugely epic games tend to fall flat. I don't think Fallout, ES, or The Witcher would really make good films. The games are so good that I don't think it would measure up.
WoW is pretty epic in the lore category, but it's still an MMO so it's got lots of wiggle room. The gameplay is based around the lore in WoW, whereas in other regular RPGs, the lore is based around the gameplay.
WoW is very linear...it's huge and you can do just about anything you want but the storyline is still rigidly linear. With games like Fallout you can create your own story and it can be different every time. Of course in a way it's linear as well but you have more of a choice than in WoW, which has the same end for each character, only by different means. I think this is why it can work as a film and why games like Fallout, ES, The Witcher, etc. would fall flat.