Not growing u in that time, I'll probably come at this a little differently from you old geezers. Why the prequels the biggest letdown in film history:
1. The acting in these movies was atrocious! Liam Neeson, Ewan McGregor, and Samuel L Jackson were the only decent actors in the series, and they were all very disappointing. And of course the movies are close to unwatchable due to the performances by ol' Hayden and Natalie.
2. The dialogue in these "films" is the worst in any movie I've ever seen.
3. CGI was heavily overused in these movies. Just because this technology was starting to look good doesn't mean you have to use it in the entire movie!
4. As DNIIM said, the lightsaber battles were way overdone. The original's battles were too boring, but the producers REALLY overcompensated.
What made the originals great was that they were the opposite of the prequels.
On to what will make or break these new movies. If these films break with cannon SW law (as laid down by the novels) there will be thousands of furious fans. Also, people would rather have a great story with good character development and acting than another movie relying on special effects. Massive CGI battles are in every movie, and the film can't use this as a lifeline.