Although I did enjoy the first movie in the series, I found that they have gotten progressively more boring. Not complaining about the CGI or fight scenes, of course--top notch, as can be expected. Direction was well done, as also can be expected from Raimi--although I found his style much more enjoyable when he was piss-poor and had a cast full of 'shemps'. My issue is with the screenplay and acting. The Parker character is just too pathetic, so every interaction is painful to watch. Also, every plot turn was wholly predictable and relied on more CGI and chase scenes rather than clever writing.
That being said, the folks behind this franchise know the magic Hollywood formula for making cash, so I cannot blame them for pumping these things out. If it was me, I suppose I would take money over art as well--at least until I had plenty of backing to do the projects that I truly wanted to do.
If you want a superhero saga with lots of comic book neato stuff with painful acting, try the last couple seasons of Smallville--at least that is free!
As for Spidey 3 - in the tradition of The Filthy Critic, I give this one 2 fingers, with the saving grace from a one-finger rating being Bruce Campbell.