Has there ever been a great prequel?

There are lots of great sequels - Terminator 2, Aliens, the Toy Stories, Empire Strikes Back, Godfather II, etc, etc.

But a good prequel? No matter what you think of the Star Wars prequels, we can agree they don't hold a candle to the originals. The Hobbit is far inferior to the LOTR, and I think it's fair to categorize those films as prequels. The Wolverine prequel was more or less panned, the 2011 Thing prequel was terrible, Prometheus is pretty controversial, Dumb and Dumberer is just plain stupid, even Monsters University was universally "meh," and anything with the word "Origins" in it is bound to be shit.

I have a theory about this, which is essentially just agreeing with Patton Oswalt: nobody cares where the stuff they like came from! Who CARES what happened to these characters when they were kids, or young folk, or what happened 30 years beforehand? Nobody! In fact, explaining everything ruins the mystery, as I would argue the idiotic ending of Prometheus did to the Xenomorph. Oh, so it was made like five minutes before Alien started? Great, it's no longer a mysterious race from the deep of space. Boring! Oh, that's how Yoda became a meditative guru on a swampy planet, just deciding suddenly out of the blue? Stupid! Oh, that's how those people died in the Thing? Lame! Prequels are just an excuse to have recognizable characters in a familiar setting, without the hassle of coming up with brand-new stories. It's like an extended introduction that nobody asked for, and was cut for good reason.

I'll admit, Godfather II is a notable exception, with plenty of DeNiro-young-Corleone badassery, but it's still also a sequel, so it's a grey area. X-Men First Class is also decent, although thankfully it doesn't end where the first one started, a true sign of a completely pointless prequel.

Have there ever been any other truly great prequels? Or can we just agree that a prequel is all-around a stupid idea?