I'm not a big fan of superhero movies, but I enjoy a few of them. And now that I saw Spider-man 2, I'd say that this was the best superhero movie I've seen so far.
Movies like this are not meant to mean a lot. You should watch them for the emotional roller-coaster ride they present. Don't think too much about the plot, everybody knows that the hero will win the day. It's fun, only if you do not overanalyze it. So, not much writing here, I'll just list the good/bad points of the movie.
The story is actually much better than the first film, and a lot better than other similar films. The action is good, all the web-slinging looks less artificial this time. Tobey Maguire does quite a good job [we actually see his face for most of the movie this time around]. Others characters also acted well, especially Alfred Molina as Doc Ock. And I really like Sam Raimi, he's one of the best directors around.
There are some really funny moments in the film. Most of the jokes are at the expense of Peter Parker. One scene in an elevetor is simply great. And Raimi keeps a lot of visual gags coming our way. He does not try to be heavy, and rarely seems to take the movie seriously.
What didn't work:
The action, especially around the end, got even more unbelievable. And I said that the plot was better than the first movie, but it's not great. And some of the dialogue is a bit cheesy.
I didn't expect it to be any different, I went to see it to spend a couple of hours having fun. If that's what you want from the movie, you'll come out happy.