Like the movie, like the art, thats really it.
I wouldn't display (or buy unless for resale) a poster with great art for a film I didn't like.
I DO however own many posters with art that I am not fond of, but for films I like OR to complete a certain collection/set.
Some may know I (not so) secretly love Doris Day/Rock Hudson films, and have a few posters, love them, but wouldn't display them.
Also as above GENERALLY speaking newer posters don't do much for me, there are of course some exceptions (although I can't think of any offhand), oh wait, an example, SCANNER DARKLY, I LOVE the Book, liked the film a lot, have a nice 1 sheet for it, I like the art. Wouldn't frame it though, I prefer vintage - not just posters, but furniture, houses, whatever - I am an old man trapped in a young body (well, um a youngish body that looks old).