The villain feels like it was ripped out of an episode of Power Rangers.
But the main problem with the villain isn't even the silliness imo. It's 1) that Green Goblin has no motivation or driving logic for being evil other than he literally took a serum or w/e that made him evil. And 2) that his origin story conveniently coincides with Spider-Man's.
But that's a common occurence with superhero films isn't it? Films like Spider Man and Batman Begins try to portray a non superhero inhabited world and show how a superhero came to exist in them. That's a pretty fanciful concept in of itself and exciting if done right. But there's always that second origin story crammed in (for the villain) so there can be a showdown at the end. As if the whole movie is just a professional wrestling match preceded by 2 hours of buildup.
Not saying it's a bad movie necessarily. I think the movie did for Spider Man what The Christopher Reeve films did for Superman. That was no small feat. Also, I love Toby Maguire as Parker.
Goblin took the serum and was forced out of the company that he built, thats his motivation.