Is Mozart one of the easiest composers to play?

Some say that Mozart is one of the easiest of all composers to play, but if this is true, how come there are so few great Mozart pianists? The easiest of Mozart pieces to play are said to be the Viennese Sonatinas. Mozart isn't too hard either.

The thing is Mozart's symphonies have an elegance. His concertos are most certainly difficult but his pianist pieces are good enough to be played by an average pianist. Mozart never tried to make music too hard like his contemporaries but he concentrated on how the music would sound.