As someone who came to the prequels pretty late, I'll say that they're pretty mediocre movies. I saw episode 1 when I was 18 in the theatre, but only cause my girlfriend at the time liked Star Wars. Personally, I'd seen the originals growing up, but by then hardly even remembered them (I was born in '81). I fucking hated episode 1 and thought it was pretty much one of the worst, most boring movies I'd seen in a theatre. I never bothered seeing 2 or 3. I decided this summer to re-watch the originals and the prequels, which I finished up last week. The original movies are dated for sure (not sure exactly which version I downloaded, but there were definitely original scenes replaced with CGI), but still reasonably entertaining. You can see why they're classics, even if they're a bit campy.
The prequels really are a lot worse. Episode 1 is still fucking awful. 2/3 were certainly better, but still had a lot of problems. A lot of the dialogue is ridiculous, some of the acting is horrible, the overall story arch is disjointed, and there's about a billion plot holes where shit just doesn't make sense. WHY THE FUCK IS LUKE GIVEN TO HIS OWN FAMILY WITH HIS OWN NAME ON THE SAME PLANET HIS SUPER EVIL DAD GREW UP ON? They're not totally without redemption, as there's some good action scenes and it was cool to see a bunch of Jedi's kicking ass.
Hopefully the new movies are in much better hands than the prequels were. It's honestly kind of shocking to look back on the prequels and reflect just how badly Lucas botched them. I mean, I can see being out of touch and making some mistakes in the finer aspects of the movies. But I just don't see how he could have so badly botched major plot points between the two sets of movies without being a complete fucking retard.