First, the reboot of Star Trek wasn't all that good. It took a timeless series of stories, that are still watched by people today, and turned it into another summer blockbuster with the chic pretty boy actors of the time, and sprinkled in a cliched action oriented story that will be forgotten long before the TOS will. When I watched it the first time I was impressed, because of the special effects mainly, I think, but watching it two years later I realized how campy it really was. It offered nothing to science fiction, and did plenty to damage the franchise.
Seconding this. The so-called movie is already forgotten pretty much. I managed to watch it by getting drunk first.
Star Wars on the other hand doesn't need a reboot, just a more serious approach to doing the movie.