Let me explain what happened to the Spidey franchise, and why there is this "reboot"...apparently, there was a big fallout between Sam Raimi (the director of the first three), Sony Pictures and Marvel Studios -- they could not settle their creative differences on where this franchise should head after 3, and Raimi was sticking to his guns in terms of his vision (which I believe was a smart decision). There were issues over money between everyone involved, and Raimi and his production team decided to just walk away.
Still, Marvel Studios was getting great pressure from the fan base to continue the series and diehard fans of the comic wanted to see the Lizard as the next big adversary, and that's when Marvel and Sony/Columbia went back to the drawing board to think of a way to take the series in a fresh direction rather than just abandon it -- I agree that this is hokey at best, and the trailers confirmed my sentiments about no one but Maguire being suited for the main role.