Not always my favorites, but IMO, ARE the greatest 6 individual solo piano works:1) Bach, Goldberg Variations2) Beethoven, Diabelli Variations3) Bach, Goldberg Variations4) Beethoven, Diabelli Variations5) Bach, Goldberg Variations6) Beethoven, Diabelli VariationsIn no particular order.If you asked for 7th work, I'd add Hammerklavier.
What's so great about the Diabelli variations? I can feel the quality of the Goldbergs, I feel so small when listening to it, something not from this planet, almost. I have the same thing with the Hammerklavier, last three beethoven sonatas, Liszt sonata, Schumann sonata etc, but not really with the Diabelli vars. What makes it so great?