Well just like you mentioned, speaking of episode I, I can't stand Jar Jar or the kid as Anakin. For episode II, I found the romance between Anakin(who grew up way to fast) and Padme extremely awkward, plus the CGI for that movie was horrible. I mean, the plots were okay, but the actors and CGI were horrible, even hard to stand at times.
If we were to talk about episode III however, it was AMAZING. The action, the actors (who did a lot better here), and even the CGI was really well handled. That's why III is my favorite from the prequels.