It's easy to blame Jar Jar for how bad the Prequels are, but it ignores the main problem: George Lucas. The man can't write or direct (he admits he can't direct). He made some pretty good actors look terrible. I like Natalie Portman, Ewen McGregor and Jimmy Smits, and they looked awful.

What saved the Original Trilogy was the story for the first one was a straight forward hero myth, and Lucas didn't write or direct the second and third. He had too much control for the Prequels.