Actually, my first thought is that you seriously underestimated the age of most of these comic book series. Marvel's are mostly from fifty years ago, except Captain America, which started during WWII. DC's big three, Batman, Superman and Wonder Woman all started during the 30's.
That's actually part of the answer. It took decades for enough fans-of-the-genre to get enough clout in Hollywood to get those comic books put into serious movies. Evn then, there's a lot of failures. (Marvel's success, I think, is due in large part to Stan Lee.)
Anyway, there's no money being made in web comics (that I know of). Therefore, Hollywood probably won't be interested.
I'm not sure that Hollywood being interested would be a good thing. For every successful and wonderful adaptation out there (Wizard of Oz, Gone with the Wind, 2001: A Space Odyssey, To Kill a Mockingbird, Harry Potter, to name a few) There are a dozen (or more) horrible bombs. Like the Green Lantern movie, the Jan Michael Vincent version of Damnation Alley, the adaptation of Susan Cooper's The Dark is Rising or the John Carter movie.
These were not only horrible movies and financial failures, they pretty much guaranteed that these wonderful books will never be made into decent movies.
All's not lost, though. The bande dessinée (or French-Belgian graphic novels) have never been super popular in the US, but the TinTin movie did well and a movie based on the even more obscure Valerian & Laureline is coming out next month.