Indiana Jones and the Kingdom of the Crystal Skull
Here is a note-perfect Indiana Jones movie; with mind-boggling chases and stunts (all real stunts, and not CGI) and a grumpily perfect Harrison Ford matched up and against friends and foes old and new. It has dozens of things to love and scream and laugh about - just exactly what you want in an Indiana Jones movie.
And then the Lucas magic takes over in the last twenty minutes or so, rendering it stupid and unbelievable. The Ark of the Covenant melting nazis? Believable, within the continuity and context of the movie. But this one?
I'm left not knowing whether to love or hate it. Curse you, Lucas!