Apocalypse Now (any version but I watched Final Cut most recently)
It's very pretty, lots of great cinematography. But as a film - an entertainment-delivery system - it's utter boredom for the majority of its 3 hours.
I've tried loads of times to watch it, Original, Redux, and this. It's just crap. The first hour or so (depending on version) is alright, but the descent into its madness and its love of soliloquy is tedious and saved only by some of the imagery - and by the ending, that's fleeting too.
No idea why it's rated so highly.
4/10, 5 at a push.
I'm off to wash my mouth out, I'm sure.