make sure that it is a flat screen anti glare CRT. My Sony G500 21" has a completely flat anti glare front and movies on it are great. Don't get a regular CRT if you are very into movies, go for a flat CRT. I know there is a certain term for the flat fronts but I can't think of it right now. If I think of it I'll post it.
If you are willing to spend a little more, go for one of those 24" cinema displays. That would be the ultimate screen for watching movies and doing everything else.