it could be contested that TPM is actually a prequel and not a sequel.
Also, I am with you on your general opinion, but I think what ruins the film is the over-long BOOOOOOOOOOOORING pod-race which goes on for like 5 hours or something......
But out of all 6 Star Wars movies it has something so brilliant that the other 5 didn't have.......Darth Maul and that spectacular light-sabre duel with ObiWan and QuiGon.