As a general rule, I think that Are rated movies should be avoided, but there may be exceptions. One R-rated movie that I would whole-heartedly recommend to any member of the Church is "The Passion." I suspect that the only reason it was rated Are was because it dealt with a religious theme and the movie industry didn't like that.
I see a lot of blood and violence in other movies that are not rated R, so I doubt whether that was really the issue. But, like I say, generally speaking, I think that R-rated movies should probably be avoided, but there may be exceptions to the general rule, such as The Passion.