Personally I am not an Opera fan, especially not when forced listening to the whole thing. I'm with Eric on the Sopranos. I do think, however, that most operas have at least one or two great songs in them and I listen to those. I agree that H.R.H. Nicole Marie does balance the heavier pieces with other music that is easier on the ears to me.
As for ballet, I love it. When I listen to classical music, my mind always associates it with some form of mental picture, be it a waterfall, a volcano erupting, pounding of the waves, birds singing, etc. Ballet transforms the music into some physical form for me and I find that satisfying.