I'd violated my usual rule and read a number of reviews before going to see Spider-Man 2, so I was expecting a surprisingly good movie. However, I've been seeing a lot of "art" films and so an action flick was pretty appealing.
Short answer: the critics are right, this movie is quite good.
What is most striking about Spider-Man 2 is that, unlike most sequels in the action-hero genre, the most interesting character on the screen is... Spider- Man. To be sure, we left the theater thinking that although Doc Oc was well played, he didn't have much depth (much less than the Green Goblin in the first film). But, he didn't need much depth to provide Spider-Man with the key elements of the plot and allow him to work through his issues.
The effects are well done, if a bit stylized; costuming is nice and the major supporting characters are all present and pretty much as you would expect them.