All just my personal opinion
Beethoven: Variations on the Minuet “à la Viganò”, WoO 68 — Mikhail Pletnev (1997), Olli Mustonen (1995), Ronald Brautigam (2011); Mendelssohn-Bartholdy: Organ Sonatas op.65 — Heinrich Gurtner (1989), Stefan Schättin (1995)
Chopin: 12 Etudes op.25 — Ashkenazy, Pollini, Sokolov, Avdeeva; Chopin: Sonata No.2 in B♭ minor, op.35 — Argerich, Askenase, Avdeeva, Pollini; Chopin: 24 Préludes, op.28 — Askenase, Pollini, Barenboim, Argerich, Sokolov, Avdeeva
Beethoven: String Quartet op.127 — comparing recordings with the following ensembles: Alban Berg Quartett (1982), Amadeus Quartet (1963), Artemis Quartet (2010), Busch Quartet (1936), Emerson String Quartet (1997), Endellion String Quartet (2008), Guarneri String Quartet (1969), Hagen Quartett (2004), LaSalle Quartet (1976), Leipziger Streichquartett (2001), Melos Quartett (1984), Quartetto Italiano (1968), Takács Quartet (2004)
Domenico Scarlatti: Keyboard Sonatas — recordings with Pieter-Jan Belder and Andreas Staier; Schubert: Masses in A♭ (D.678) and E♭ (D.950) — Nikolaus Harnoncourt, Chamber Orchestra of Europe, Arnold Schoenberg Choir