Successful comic book titles are potentially worth big money, and it doesn't take a comic fan to notice how popular they've become. Movies based on characters like The Avengers, Batman, Spider-Man, Superman or The Guardians Of The Galaxy are bringing in millions to their parent studios, and packing movie theaters all over the world.
And despite what may appear to be the case, Marvel and DC aren't the only comic companies out there who's characters have made the transition to features. Others, such as Dark Horse have also made the leap, with characters like Barb Wire and Hellboy – the Predator and Alien franchises are licensed to Dark Horse as well, though they're based on pre-existing movies.
Though that's not to imply that that there're aren't even more, such as Image (Spawn), Avatar Press (Faust: Love Of The Damned) and Malibu Comics–which was purchased by Marvel–though they haven't been nearly as successful.
If you happen to be Legendary Pictures, with no comic titles of your own, you take the example of Stacker Pentecost, and create your own. In the movie space they have found success most recently with their reboot of Toho's Godzilla, and Pacific Rim (the sequel being produced with Universal Pictures, as opposed to Warner Bros) though they have had no options as far as superhero comics go (though, since they're partnering with Universal Pictures they could potentially produce a movie based on Marvel's Namor, The Sub-Mariner, which as far as I am aware Universal owns the license to).
Though with titles from Legendary Comics like The Tower Chronicles, Shadow Walk, A Town Called Dragon, Annihilator and Epochalypse you can be sure that one of them–or perhaps a Legendary title yet to be unveiled–that will eventually make the transition to features.