Batman has been blessed with some very, very good writers who revived the character and re-imagined him. They also returned Bats to his roots by making him a detective again and providing a non-homosexual reason for having a "Robin." That was a pretty tall order and O'Neil and Miller pulled it off well (pardon the pun). Because of the way Bats has been positioned, they can continue to mine the detective/mystery/supernatural thing for years to come. Mysteries, in particular, have a lot of staying power in the market place (think Sherlock Holmes and Agatha Christie). Even so, Bats is still likely to go through several future iterations (until DC loses the copyright on him, like poor ol' Popeye the Sailor Man). If you notice, most Batman books are about Batman, but as reflected off other characters. Those characters (the Joker, Catwoman, and what-not) are the stars, but something about them, the way they are, tells us something about Batman.
ASM is much more about Pete, front and center, it always has been. Bruce Wayne was pretty much a blank slate upon which writers could force meaning. It's much harder to do with Pete, as he has a more well-defined character. It also has made it tough for Marvel to re-invent the character or to allow him to "age" much. In the end, the marriage didn't really "evolve" Pete. He was just as stuck in the marriage as he was when he was single. He wasn't ever going to have a teenage daughter in 616 continuity. If they really wanted to develop him, they would let him age, marry him off, have him lose a leg, stop crime fighting, le his daughter take over, etc. That would make for a more interesting character arc, but it can't happen. Batman can change to meet the era, because no one cares about Bruce Wayne, he's little more than a charicature. We don't "identify" with Batman, we fantasize about being him or we are entertained by him. We can have dark Bats, clown Bats, gay Bats, whatever. Spider-Man's not about Spider-Man, at its core, it's about Peter Parker. Originally, high school kids and college kids were supposed to identify with Pete. And they did. But when kids grow up, they can't identify with him as much anymore. It's like your friend who can't stop talking about how great high school was. But if Pete's suddenly a married guy with teenage kids, kids don't identify with him so much. Suddenly it's about paying bills and keeping a marriage together, the territory of serious adult fiction. Any story about a human being gets tricky when that person doesn't grow and develop. But corporate interests prevent that from happening. How long has Bart Simpson been whatever age he is? Will Pebles and Bam-Bam (aside from that one awful cartoon) always be babies? Maybe Marvel will, one day, go the route of Wolverine, and make non-aging part of Pete's deal, and just allow certain cast members to age around him. Hard to say. But it WILL be interesting, when all of us on this board have entered our 70th decade of life, to see what Pete looks like, just like it's interesting for an older generation to see Bats and Supes all grown up (not).