OK, here goes...
A New Hope vs TMP- A New Hope, by a hair, I love TMP, it was written by one of my favorite authors, Alan Dean Foster, and it is told very much in his style.
Empire vs Kahn0- Empire, hands down.
Jedi vs Spock- Jedi, would be a landslide if it wasn't for the fucking Ewocks, god I fucking hated those little furballs. Give me an industrial blender and an Ewock and I'll have some fun, feet first style.
Menace vs The Voyage Home- Voyage Home, Mecace was an afterbirth of a movie.
Clones vs Frontier- Going with frontier, but a bit closer.\
ROTS vs TUC- ROTS, with the exception of the love scenes and general cheesiness, I loved this flick.