In my opinion:
There are MANY difference between X-Men and Superman, not at all alike.
X-Men is a group of heroes in a realistic world with the center being predjudices.
Superman is a movie about one hero in a mythological fantasy world with the centering being Superman (and all the aspects of Superman) and the characters around him.
I can see what you're saying. But, to me that's like comparing apples to oranges. Because yes, both are superhero films- but, that's more or less the only thing both 'worlds' have in common.
X2 was better than X1, similarly to how SM2 is better than SM1, etc., etc. Finding faults in the first and fixing it for the second.
Yes, Singer has directed X-Men films. But, this is his first time with a Superman film. Take that for what you will.
Oh an um- btw, since when did I throw crap at Ang Lee? Don't know if you're generalizing or not. If given a second go, I'm betting Ang Lee would have seen where he went wrong and fixed it while further improving what he got right. And yes \/ same goes for Tim Story as well- first F4, it was good and had some faults- which I think will be fixed for the sequel. I apply this to ALL first films and their respective directors. To me, first films in a trilogy, are a "test"- find the faults, find the strengths; improve upon the strengths, fix the flaws. And alot of the time- this is what happens.