I am generally okay with villainous resurrections, but the problem with Norman. . . well, okay, there are a lot of problems with Norman. *ahem* However, a few that really stand out:
1. Norman Osborne didn't just die, he died establishing a villainous legacy. He was the first Goblin but not the last, with both "Harry becoming the new Green Goblin as part of a complex, broken relationship with both his deceased father and best friend" and "The mystery of the Hobgoblin" being standout parts. Bringing Norman back to life kind of devalues all the stuff that happened later following his death.
2. The entire plot arc that brought Norman back to life was, simply put, kind of trash. There is a reason people talk about the Clone Saga with such disdain. If you want to bring a villain back, fine, but you shouldn't bring them back with a complete nonsense storyline, and then *firmly tie said villain's new status quo to that storyline*. Which is more or less the case, because the entire concept of Grand Mastermind Norman Osborne isn't part of his original characterization, its entirely an artifact of the Clone Saga "I am the architect of all your woes" retcons.
3. Speaking of which, "I am the architect of all your woes" is almost always a terrible angle for a character. Its cheap heat, and inevitably forces one of two bad outcomes: either The Villain Wins, because you've made them so omnipresent that they can't possibly lose; or The Villain Forgets To Win, because you've done that but have the hero arbitrarily win anyway. Either way, not satisfying.
It feels like a case of. . . Norman Osborne is important in everyone's eyes because of The Death of Gwen Stacy. Since he's such an important part of the mythos, someone decided such an important character must both be alive, *and have in-setting importance and influence in proportion to their out-of-setting reputation*. Which is a bad idea we are still stuck with.