Doh!!! What a GOOD question... I like The Empire Strikes Back (Episode V), but Revenge of the Sith (Episode III) was just excellent, a link between my times and those of the Original Trilogy that I never lived...

I think it'd be a draw between episodes III and V, but I voted V for 2 reasons: 1) in the poll Ep III was beating Ep V just for 1 vote, 2) There is a crucial "I am your father" in Ep V...