I've not actually gone to see it yet, but I'm expecting typical JJ Abrams fair. He's very good at taking one or two other movies, plagarising them like crazy, pasting lens flare all over them, making them fun and then saying the word 'homage' as much as possible in interviews so no-one calls him out over the lack of anything original. I expect it'll be entertaining, but I'm not exactly hoping it'll change my life or have a massive impact on cinema. But the prequels were actually just bad movies.
The Phantom Menace wants to be a political thriller, but Lucas clearly doesn't actually know how to make one. He failed to explain any politics and mostly just created a confused mess where everyone works against their own interests because, you know, politics is confusing. It ended up being a set of disjointed storylines that were only vaguely related. A greater focus on the senate would've made a better movie, but wouldn't have sold as much merchandise, so instead we get Jar Jar Binks, who makes a good plushie for the 3-6es.
The same thing happens to Attack of the Clones, which is equally bastardized between a dozen genres. There's a love story in there somewhere, though it's incredibly cack-handed, poorly written (Skywalker in particular sounds like a rape-y psychopath trying to learn about human emotions from someone he's abducted) and kind of jammed into about 30 minutes of screen time so it has less depth than the plot of Bridesmaids. There's some kind of politics-y thing happening, but no-one understands any of that because politics is confusing so we don't look at it for long enough to explain it. And then there's lightsabres and things, because this is a Star Wars movie and so there has to be a ludicrously over-choreographed lightsaber fight, even though the lightsaber fights in the original films had barely any choreography and the entire point in ALL THREE was the larger meaning. Episode 4's lightsaber fight was Ben sacrificing himself to save the others, Episode 5's was the big father reveal, and Episode 6's was the denouement of the entire series.
Finally, you had Revenge of the Sith, which was better than the other two but still not a very good film. The problems for this one are mostly because the entire film devolves into a mad dash to tick all the boxes needed for Episode 4. Anakin, played by the simply dire Hayden Christiansen, has the emotional intelligence of a brick, and so his descent to the dark side mostly takes place through a series of constipated faces. Then lightsabers, again without any deeper meaning going on, including a horribly disfigured old man going up against a CGI puppet while performing a production of Swan Lake. Then pretty much the last 2/3rds of the movie is a desperate rush to try and get everyone where they need to be before time runs out - Yoda has to get to Dagoba, the kids have to be born and Amadala needs to die, Anakin must become Darth Vader, the Emperor has to go full Dark Side and take over the universe (which appears to happen in about 20 seconds), all the Jedi need to die (another 20 seconds or so), the Death Star needs to appear for god knows why, the droids need to be aboard the same damn ship that they're still on 20 YEARS LATER. Some of this stuff could've been left out. There was no need to kill all the Jedi in one stroke - they were scattered around the galaxy and could be hunted down in the 20 years between the films - hell, that's meant to be what Vader is doing. Why the hell was the Death Star included? There was no sane reason to put that in. Yoda doesn't need to telegraph that he's off to Dagoba. This is just frenzied box-ticking, and the movie suffers from it. I'm always left with the impression that no-one did anything over the intervening time because in it's rush, RotS leaves nothing undone; more actual events appear to happen in the 1 year between episode 4 and 5 than the gap between the prequels and the original movies.
I rate Return of the Jedi and Revenge of the Sith about equal, and that's kind of where I expect TFA to be. As long as it has a reasonably coherent storyline, it'll be doing better that 1 and 2.