Films built for a room that talks
You need a film that survives commentary
Group viewing is a social event with a film attached. People will talk, and the question is whether the film is ruined by that or improved. Broad comedies, heists, disaster films and enjoyable nonsense all get better with running commentary; delicate character work does not.
The kindest thing you can do for a great quiet film is not put it on in front of six people.
Familiar beats new
A film half the room has seen is usually the better group choice. The people who know it become an audience for the people who do not, reactions are anticipated, and nobody has to concentrate to keep up. New films split a room into those following it and those who have quietly given up.
The exception is a film everyone has heard of and nobody has seen. That shared position is its own kind of fun and worth engineering when you can.
Decide fast and commit
The browsing is the worst part of the evening and it scales terribly — six people with veto power will not converge. Somebody should pick, out loud, within five minutes, and everyone else should accept it.
Use this list as the shortlist to pick from. Its ordering reflects how large audiences responded, which is as close to a group-tested ranking as you can get.