When "Catwoman" came out, I pointed out that its major failing wasn't its awful story or casting, it was the fact that it had changed too much of its mythos to *be* a Catwoman movie. Most people, for instance, can give you the basics about Batman - rich guy, parents killed in front of him when he was young, butler, hep toys, world class mind, and so on. If they made a Batman movie where he was running around with twin .45s akimbo leaping sideways while blazing away with doves flying behind him, we'd all right get fairly angry, since Bruce's views on guns are fairly known. Catwoman, the movie, changed too much of that stuff to make it even a mediocre movie.
Comic book fans are used to retcons, fanwanking, multiple continutiies and so on and have been for decades. But all we ask are the basic elements of the mythos be there, and we can roll with a fair amount of stuff. Reintrepretation of the basics is a well-honed chestnut of the comic industry. You know that iconic shot of Bruce's mom's pearl necklace spilling over and him in the circle of light with his dead parents? Only came about in the early 80s, but it is entirely subsumed now and one of those iconic mythos elements. We can roll with these things, and those who can't are the ones who *are* those Comic Book Store Guys.
There is something to the argument also that comic book movies drive a percentage of fans farther back to the original source, namely comics. With Spiderman 3 out, I've spent the last two weeks or so fielding Venom and Green Goblin x4 questions, heh. But a couple of people I pointed to specifics and they are tracking them down. The most fun I had was explaining the 1985 Crisis of Infinite Worlds, cause it's pretty fun to basically say "Yeah, basically DC? wiped the previous fifty odd years of comics, so start Post-Crisis." :) Marvel, you've got one long continuity that's hard to suffer through the earliest comics.
So I guess my point is, at least for me and a bunch of people I hang with, comic book movies that stick close to the basic mythos and doesn't radically change those essential elements are the ones weare happiest with, even if the other changes are radical. Batman Begins, for instance, has that wacky-ass Batmobile ATV thing, but they got Batman and his earlier experiences fairly accurate, so you bend with it. This is, incidentally, why I will be able to carry myself through the Transformers movie, specifically because, much like the X-Men movies, I hold it in a different continuity bubble than I do the old show.