The problem, to me anyway, is that the prequels just don't look "real". There is way too much CGI going on in the backgrounds and it all just seems very cartoony and busy.
If you look at old-school movies, explosions were actually that - explosions. Nowadays they are computer-generated. Now don't get me wrong, a lot of CGI stuff looks absolutely amazing, but some, no matter how much they try, just doesn't. Look at the battle between the Trade Federation Droids and the Gungans. I can't be alone in not caring one whit about that because there were. No Actors. At. All involved in that battle. Just CGI. It's hard to care about people when the people aren't real, lol.
I'm not sure if I'm adequately expressing what I mean, but hopefully you guys understand. Anyways, just my opinion.