On a music theory level: Why is Russian Romantic music loved? Why Hungarian music as well?

Monday, September 6th, 2010 at 2:28 am

Why are they considered to be so attractive? Do they convey more emotion through their harmonies, dynamics, and rythms?
What sets classic Motzart pieces appart from Mussorgsky, Liszt, or Rimsky Korsakov pieces?
What is the difference in composition or delivery between these types?