A list of movies that either show an important part of the DC Universe, or just ones that'll leave you wishing it had a sequel:

Justice League: The Flashpoint Paradox~ What would have happened if Barry never became the Flash? Find out in this amazing movie.

Justice League: Doom~ Even Superman has a weakness, and it's duly noted in this movie about a surprising change of events.

Justice League: Crisis on two Earths~ Crime Syndicate VS Justice League. All that needs to be said.

Batman: Under the Red Hood~ The story of Jason Todd and a massive turn of events to change the Bats life forever.

Green Lantern: It just sucked. Point blank. It was really, really bad. I saw a microphone at one point. I added it to the list because it was so bad.

Teen Titans: Trouble in Tokyo~ Not Justice League related like most other movies on here, but it's got that same serious vibe, while still holding true to the humor of the Teen Titans.

Avengers. Nuf said (totally in a good way)

Xmen (all of them) . Nuf said (^_^ ditto)

These are the movies I've watched completely, and I'll add more as I go on.