-Needed a new protagonist. You can't have two-thirds of one trilogy about Anakin, the next trilogy about Luke and then have the whole thing about Anakin. It's all or nothing. The focus of the first should move to Obi-Wan.
-Needed real sets/characters. I don't care how state of the art their CGI is, it looks very fake. I can live with ANH's wolfman, but Jar Jar looks painted on. Even now the OT aliens hold up. Some of them look goofy, but it just adds to the charm.
-Needed a different writer. Not to be mean, but I have a hard time believing that anyone read over that script. Even GL. The plot, dialoge... All of it. It was just garbage. It contradicted itself and the OT so many times that I have to just assume that he's never watched the original movies.
-Needed to get rid of the OT allusions: We don't need to see Boba, baby Greedo, Yoda, Jabba, Vader in his suit, C3-PO, R2-D2, Luke or Leia (I think I'm forgetting some...) to know what series we're watching. That's not a clever in-joke to all the Star Wars fans, that's... for lack of a decent vocabulary, stupid. Feels like they're using them for support. And... well, they are.
-Needed to stop ruining all the big surprises/plot points that make up the OT. It's a completely different trilogy. Make up some new material. It wouldn't have been that hard to side step most (and by most, I mean all) of those.
-Needed to tone down the fantasy and make the fights look a lot more realistic. It's all Jedi, twirling around yelling out puns. Remember the invasion of Hoth? The attacks on the Death Star? Now those were fight scenes.
-Needed to stop switching Sith every movie. Pick one and stick with him.
-Needed to lose the prophecy bulls**t. Someone, thousands of years ago, foresaw that Anakin would be born and that he would bring balance to the Force for about twenty years? Give me a break.
-Padme shouldn't have died just because she's sad. That doesn't make sense and that rips another hole in the continuity.
-Needed to drastically reduce the number of Jedi. Enh... It's too late to explain this one.
-Needed to cut out the midichlorians (sp?). Obviously.