There's the exotic factor, of course, but manga is generally (with a few exceptions, like Golgo 13) written by a single author, so there's a single coherent story the entire way through.
More, manga eventually ends, and has larger changes to the status quo. Batman, as a character, hasn't fundamentally changed since his inception. While everyone will laugh and throw fedoras at me for mentioning Naruto, I'll point out that Naruto has settled down, raised a family, and eventually been crowned Ninja Jesus and President of the World. That's canonical, by the way - It's not an imaginary story or an alternate universe, the character has permanently changed.
And now, this is just me, but I've noticed something in comics (at least in Marvel and DC). In comics, characters don't really fight as much. Or rather, the actual physical clash very rarely matters. Check out the storytime for Green Lantern, where Hal fights the Dawnbreaker: You'll notice that the outcome of the fight is abruptly off-screened, where a manga would have a long, elaborate battle of constructs and fisticuffs that would eventually climax with one guy getting beaten down. Here, the conversation IS the entire fight, and Hal goes down immediately afterwards.
Contrast that to the volume-long battle against Dio in Jojo's Bizarre Adventure, or the Arima versus Haise duel in Tokyo Ghoul. Those ran for multiple CHAPTERS, and the outcome was determined not by the person who had the moral high ground, but by the guy who could beat the shit out of the other dude. As a reader, you feel there's more value for money.
Finally, manga tends to be more conservative than comics. As you know, pushing a message doesn't work well with entertainment, and manga doesn't tend to push a political or social message. That's why it's simply more fun to read. Even non-action manga like Ikigami (A government employee delivers Notice of Deaths to people who are about to die) don't preach.