They should have rebooted the series with the 2nd movie IMO, which was absolutely horrible, then 3 came out and made things even worse.
Sam Raimi just got the character of Spider-Man way too wrong. Yeah, Tobey played the timid/nerdy Peter Parker side fairly well I guess, but when Peter Parker puts on his Spider-Man mask he should be a wise-cracking/sarcastic/witty jackass that irritates the hell out of his enemies. Instead we got a deadpan Spider-Man, which was surprising considering Sam Raimi's Evil Dead films with the wise-cracking Ash. Also, the villains were portrayed as way too tragic or sympathetic for my tastes. Out of all the villains they had, Harry Osborn/Green Goblin II should have been the only one who had a chance of actually being redeemed.
And as for Spider-Man 3....well, that again completely warrants a reboot. They destroyed Spider-Man's entire motivation for being a hero essentially and fucked up Venom at the same time. Personally though, I like the fact that they're going back to high school, and I hope they get a young up and coming actor like with the upcoming movie Kick-Ass and its main character to play Spider-Man, that way you can actually show him grow from a teenager to an adult superhero in multiple sequels like in the comic itself.
They just need to go back to the comic's roots and everything should be cool.