Spider-Man 3 terrible for two reasons (at least): Dancing Emo/KD Lang Spidey, and the Exposition News Channel setting up the third act. There's many, many more reasons but those or the two bigger ones, for me.
And really, I think it retroactively makes the others movies not "as good" as they were when they came out because it sort of sums up the tone of the Rami movies.
TASM was far from "perfect" and certainly has its own flaws but I think I liked the tone and how they treated the characters more, better fits in the current climate of how comic-book movies are. A bit more seriously than action scenes and villain/hero confrontation scenes that look like they were taken from a Power Rangers movies.