It's because he knows the meaning of responsibility, and not only does he understand what it means to do the right thing for the right reasons. He can teach this same thing to others. He's intelligent, kind, compassionate, adorkable, in short, he's everything that Spider-Man should be.
And on top of that, I love the new female character that the writer's been using. Chat is a fully fleshed out character, who can be sweet, annoying and most of all, who can be all those things at the same time. She's not just a bit of cheesecake to show off for the boys. She's not an annoying bimbo, or a bitch or...
She's a person, with flaws and strengths who can be funny and compassionate and though I doubt that her and Peter dating would really work, for several reasons, I still like seeing scenes between her and Peter.
In short, why can't the writers of ASM take a hint or ten from MA in how to handle Spidey?