It had so much potential, and while I was expecting a mediocre -to-good movie (like the last one), I was still expecting entertainment. It wasn't entirely disappointing, but there was a lot wrong with it.

Basically, there's a reason the percent of people that liked it on Rotten Tomatoes looks like this:
Spider-Man 3: 61%
Spider-Man 2: 93%
Spider-Man : 90%

Here's what didn't work:
Apparently Venom makes Spider-man look emo. That was ridiculous. Who thought that would be a good idea?

Spider-man is supposed to be visibly affected by Venom. He acts rude and cocky because of the power and the influence of Venom. But that definitely doesn't mean he starts acting like he's living the 70's and starts creeping everybody out. This part of the movie had the entire audience laughing, and not in a good way. Everything about how his behavior was influenced during this portion (there's a specific part...in the rest of it he does act like he should) was completely ridiculous.

Sandman's sudden confession felt totally wrong. There wasn't enough to compel him to stop all of a sudden. It felt way too artificial. Suddenly everyone's dying/vulnerable and Sandman decides to play nice and give up? Please.

Kirsten Dunst singing? Should have brought some earplugs.

Tobey Maguire can't cry for shit. Seriously, it was laughable. Really, the audience was laughing. It was that bad. It didn't help that they made him cry all the time.

All that said, there was some good stuff that made the viewing worthwhile. Namely, all the CGI with Venom and Sandman was incredible. There is no question that these are some amazing effects.

Spider-man destroying Venom was amazing.

Spider-man's other love interest was hotter than Kirsten Dunst.

In a nutshell, the review from The New York Times put it best: "Aesthetically and conceptually wrung out, fizzled rather than fizzy, this latest installment in the spider-bites-boy adventure story shoots high, swings low and every so often hits the sweet spot, but mostly just plods and plods along."