Its a regularly discussed subject mate : "who could do better than Moyes".
Unfortunatly the answer is totally subjective, there is no right or wrong answer, everyone has their own opinion on it and it seems thats you think there is no manager who could have done better, or could do better than Moyes has and your mind is made up.
There are numerous managers in football around the world, but whenever they get suggested as a possible alternative to Moyes its the same excuses that get used : "they'd never come here", "they need money" , "they got so and so relegated" , "they'd never put up with Kenwright", "they've never done exactly the same as Moyes therefor never could" and so on.
Its all ifs and buts, and the only way to ever know if a different manager could do things better is to actually make the change (not that i'm advocating it). There are numerous managers who have at this stage a better cv than Moyes had when we appointed him, sure it doesn't mean that all of them could do better but it shows how ridiculous it is to write off more experienced and successful managers and say they couldn't do what an inexperienced unproven manager could.
And yes, whilst what Moyes has done at Everton has not been replicated elsewhere neither have the exact curcumstances he done it under, so many differing factors as well as a managers ability determine how well they do in a job. For example, Di Matteo once had WBA on a run of 1 win in 12, yet he's now a FA cup and Champions League winner, so does that mean he's gash or awesome? Neither, cause its not as simple as that.
So there you go, if you think Moyes is the only man who could do what he done/does then fair enough, but plenty of people don't and we'll never know who's right.