milliways-bar
Like all good heroes, Peter Parker was set on his path by the tragic death of his role model and legal guardian. When he first got his powers, he used them in the pursuit of fame and fortune... the only way, he thought, a poor orphan from Queens could ever get either. But as everyone knows, his Uncle Ben was killed by a robber that Spider-Man himself could have stopped, and thus, the teenager finally understood -- with great power, there must also come great responsibility.
This philosophy is open to interpretation, but at the core of it is the belief that if you can do something to help people, especially something that no one else can do, then you should. It's this belief that still motivates Peter. He expects the same from other superheroes, too, and no matter how many times he's let down on that front, he continues to believe that they will always, ultimately, do the right thing. He never fails to be disappointed when they don't -- even if he acts cynical on the outside, even if he pretends he never had that faith in them. It's often this very idealism that influences other heroes, that causes them to trust Spidey without much debate. As Cap once said: Peter's a bad liar. He has too much respect for the truth.
(Even villains earn this disappointment sometimes. He never expects them to do the right thing, but still manages to be horrified when they sink to new lows.)
Doing the right thing isn't always the same as obeying the letter of the law, of course, which is something that will never stop causing trouble (and sleepless nights) for Peter. Spider-Man's had almost as much bad press as the X-Men (some justified, most not), and is notoriously unlucky with the police. Half hate him as much as the bad guys, half tolerate him, and the few that actually like him? Tend to get killed.
Between the Daily Bugle, the NYPD, and the bad guys who do things like clone him, kidnap his aunt and wife, kill his unborn child, etc, Peter's had enough reasons to hang up his tights. He's even done it a few times. But he always goes back to being Spidey -- partly because of the power/responsibility thing, and partly because ... it's an addiction. Liberating. The mask hides his face but lets him be who he really is, gives him the freedom to joke around legends like Captain America, to save lives and make a difference. Sometimes, he's more comfortable as Spider-Man than as Peter Parker. When he can be both at once? Well, occasionally he needs that so much that he'll even talk to Norman "Green Goblin" Osborn (after punching him in the face a few times), but the best times are with MJ, Aunt May, and the Avengers. Right now, he has an extended family around whom he can be himself, and life is pretty good.
Naturally, this won't last.