Hollywood has it's creators, comic books have there's. For a long time now, no matter how good an adaptation was, it ALWAYS fell short of the comic books(that includes the Bat films).
What's special about Whedon is that tmr, this guy could write a superman book, and it may go down as one of the best runs ever...He's already done it on Xmen and that's a book known for it's legendary runs, he stepped in and smashed them(imo). He really is that dude. And for the first time ever, they gave both writing and directing control to such a person? I've payed very close attention to the type of response Avengers has been receiving and what I've found hasn't surprised me in the slightest. The reaction the film audience is having is very much the same as the reaction the geek community has of a great comic book. People talking about moments and who's stronger than who and new favorite characters...Cap has multiple moments where he's doubted as a leader and simply takes charge by example, I've seen so many people talk about this the way I used to talk about it when I first started enjoying Cap(he was bland to me before that). People are experiencing with this film what I experienced the day I stopped being DC exclusive. Before that day most marvel characters(outside X men) were bland to me, and I feel that's what's been going on with the response to the films thus far. "Ok, I see why cap is a bad ass, I see why hulk really is so special...etc"
The thing about Hollywood is that these guys can't hang in the comic book world. I just don't see Singer or even Raimi writing a solid comic book. With the exception of Goyer and Lindelof, who have written a book or two, but even these two guys aren't capable(thus far) of a legendary run(on their own anyways).
What makes Avengers such a powerhouse is that even as a comic book it's better than a lot of it's source material, some have even said it's the best Avengers they've seen anywhere(see totally rad show). Outside of Blade, I've honestly never seen that happen.
I hope Marvel keeps this approach in mind moving forward. Your films do the best when they can actually hang with the source material.