Said it before and I'll say it again, thing that separates him from the likes of Valencia.. is attitude pure and simple. Bale might be deluded in his quest to be the best player in the world and does alot of daft shit, but the kid is ambitious.. he's dedicated to improving, that can only ever be a good thing.
There are several things that separate him from Valencia. One example being that Bale has worked on improving his right foot and is now comfortable in using it to cross or finish with it when the chance arises, Valencia just refuses to even contemplate improving his left foot.