It's Schindler's List for me. Makes me feel like an unserious movie fan (and human in general), which is what prompts my question. Even though it's an all-time classic, it's also very long and presumably quite sad — not easy to motivate for that combo.
I suppose Liam Neeson would be annoyed to learn that anyone is more excited to see his Frank Drebin than his Oskar Schindler.