Well, I don't know how to quantify it on a scale of 1-10, but I've seen your suggested film (in fact, I own a copy of the Criterion Collection edition on DVD) and I love it. It's one of my favorite films. I've seen movies that rove back and forth over larger settings, but in the end leave on thinking "That's IT?!" Contrariwise, 12 Angry Men packs a complete and compelling tale into a single room, and in fact plays on the contained setting in order to heighten tension. Just an all-around good film. I recommend it.

My suggestion:
http://www.imdb.com/title/tt0085859/

>>599
I'm slightly confused by what I've just watched. As near as I can figure it was a commentary about 80s life for the "red suspenders" brigade, noting the emptiness of Mac's life despite the fact that he earns 80k a year with 50k something or other. He has no luck with the ladies or friends, and returns to an empty house at the end. Unfortunately I didn't live through the 80s so it was lost on me. I just feel sort of depressed now I've seen it, I'm not sure if that was the emotion it was going for.

Suggestion:
http://www.imdb.com/title/tt0240510/

Of the three suggestions so far I've only seen 12 Angry Men. Truly an incredible film. I tend to have a strange taste in film though. I understand and can identify films which are technically good. That is to say, films which are by all objective metrics decided upon to be good. But I find that so many modern TV shows and films, while technically perfect, seem to be lacking something. They're well filmed and well written but have no soul, for lack of a better expression. So while I appreciate technical superiority and take it into account, my favorite films tend to be those full of that incommunicable essence of life. Films that make you want to stop watching films and go out and be alive.

Ralph Bakshi is one of my favorite directors. I'd recommend all of his films but if I had to pick just one it would be American Pop.
http://www.imdb.com/title/tt0082009/