I hate having to still explain this, so I'm going to do it in Bold face so everyone gets it:
A LOT OF COMIC BOOK OUTFITS WOULD LOOK FUCKING STUPID ON SCREEN!
There are some that'll work, some that'll do fine and some that will sink the entire movie if they show up wearing them and a very small number which look stupid even in context of the comic. Hawkeye will not be wearing purple because it would look idiotic and I hope to god they lose the stupid mask too. Wolverine's costume is that rare kind of costume that would get the amazing "Costume problem" trifecta:
1) Make the movie IMPOSSIBLE to take seriously
2) Add a fairly solid extra amount to the budget
3) Add an extra month to the production time, due to the time lost putting it on and getting it off.
As for Batman, all the comics have said or suggested that he wears Kevlar (it would strain believability if he didn't) and I've got news for you: That's what he would HAVE to wear. Does it have some visual problems, sure. Is it better than being asked to believe that "No really, this cloth is bullet proof." Yeah it is.
Lastly, I'm sorry but costume is ultimately unimportant. Iron Man could be spray-painted black, and I wouldn't care so long as the writing was solid, the action was good and the actors did their job well. Daredevil and Fantastic 4 had fairly true-to-the-comics outfits and that didn't stop them from being mediocre and complete shit, respectively. And I sure as hell didn't hear you complaining when Doc Ock showed up in Spider-Man 2 in a trenchcoat instead of green spandex

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