My list is almost the same as Susan's and bizarre_eye's, with these films eliciting a response of 'You enjoy this? Really?' amongst different groups of people.
- An American in Paris
- Flash Gordon
- Citizen Kane
- My Best Friend's Wedding
- Plan 9 from Outer Space
- Jason X
- The SpongeBob SquarePants Movie
- Night of the Lepus
- Nude on the Moon
- Troll 2
I could watch all of these repeatedly – and have done – and enjoy them all on different levels. I know people say Citizen Kane is an old one because it is generally regarded as the greatest film ever made, but most regarded as something for film scholars and critics, rather than something which is actually entertaining.