When the final movie in the first Spider-Man trilogy changed Peter Parker's motivational motto from "With great power comes great responsibility" to "shit happens" was the perfect moment to call for a do-over. Let's see what other Cinema Sins Spider-Man 3 committed.
Judging from the positive reviews of The Amazing Spider-Man 2, the notion that a superhero movie can't support multiple villains has been tossed out, giving Spider-Man 3 no excuse — it's just a bad movie.