He's often mid-air with no chance to maneuver when he gets hit.
Yes, he can be hit, and has been hit many times by numerous foes. But for every punch he takes, there's at least five or six instances of him dodging multiple bullets, energy blasts, or punches. Early on everyone hit him. Nowadays it requires an incredibly quick opponent or a plot device (often a person in danger) for him to be hit. He's gone multiple fights without being touched.
So it's both less powerful than the fanboys would think, and more powerful than the dissenters want to believe.
I'm starting a Spidey Respect thread soon (with tons of scans). That should reinforce some of my points.