I actually like the idea that seems to be used in x-men. Use the basis, have it closely relate to the comic, but use the main storyline something new (that fits in with the universe already establised by the comic). And obviously the origin story for superheros usually can be translated into a pretty good movie (just not so much in Hulk, sorry...it was long and drawn out, not enough Hulk)
As far as unknown actors. I honestly have to agree with it. I mean the problem with getting a new batman for instance is that who fits as batman? Keaton does. Same thing with superman, its Reeves. Then if you take some highly known actor, its too jarring and usually doesnt fit as the character. Tom Cruise as superman or batman. Stuff like that...just doenst work in my opinion. I mean who really cares if you dont know the actor. As long as they are a good actor then there is no problem. studios like to use big names because it draws crowds, first you already have that with a comic book movie (get a good chunk of the comic crowd) second, i say give me a good story with good actors and im there, doesnt need to be super famous actors
-Darth Simon