Gotta go with chronological.
The trouble with superhero films is that they are made to essentially broaden the appeal of a genre character or characters. Yes, the studios want to appease the hardcore fans, but at the end of the day, they also understand that they need to turn a profit and make the film appealing to a wide audience. And I have no problem with this. If it means I never get to see Batman in his classic blue & grey costume onscreen or I Spider-Man never has his man-made webshooters, then so be it. These films need to be audience accessible so that people don't just view them as a "geek thing."
And the best way to tell a story that you're trying to make easier for a wide audience to understand and be immersed in is to start a the beginning. Take, for example, Batman Begins and Tim Burton's Batman. Both are solid movies and were big hits. But one of the major complaints about the Burton film was that it was a movie about the Joker. Granted, a lot of that has to do with the fact that they gave Jack Nicholson so much screentime. But also, they made Batman the mystery, while giving us the story of the Joker chronologically. It's an interesting technique but I think it was really detrimental to the film. Batman should not be the mystery because the movie should be ABOUT Batman. It shouldn't be about a bunch of people trying to figure him out. That's why Batman Begins works so well because it takes us back to Bruce Wayne as he creates the Batman persona, instead of never even addressing why he chose the mantle of the bat besides his parents getting plugged in an alleyway.