Well the longest movie ever made, is a movie called "The Cure for Insomnia"<--- 89 hours. However i've never been unfortunate enough to see it.
My longest: Actual: Prolly (like erbody else) LOTR Felt Like: FREAKING PIRATES 3!! My god, that felt like 6 hours, i was soooooo ready for it to end, an hour and 20 minutes before it did *throws up* god it was bad.
Probably LOTR, although I have seen Titanic too. I also saw Gone with the Wind when I was little, and when you're young that movie seems to go on forever.