I recently watched Gladiator again and I kept thinking to myself how glorious the ending was. Which led me to the conclusion of how endings are great when the main character dies in some self-sacrificing way. Examples: Armageddon, Code Geass (Probably the greatest ending I've ever seen), Eagle Eye (almost. it looked like he died, which made it good), and... uhhh I guess that's it.
My movie theory is that if the main character dies, then the movie is epic. With the exception of failure directors and movie plots. What it basically means is that what separates a good movie to an exceptional one is the life and death of the main character.