All just my personal opinion
Beethoven: Cello Sonatas — Summary for comparisons of recordings, involving the following artists: Casals/Horszowski, Casals/Schulhof, Fournier/Schnabel, Fournier/Gulda, Fournier/Kempff, Harrell/Ashkenazy, Isserlis/Levin, Maisky/Argerich, Perényi/Schiff, Queyras/Melnikov, Rostropovich/Richter, Wispelwey/Komen, Wispelwey/Lazić
Beethoven: Piano Sonatas — summary for comparisons of recordings, involving the following artists: Wilhelm Backhaus, Paul Badura-Skoda, Daniel Barenboim, Ronald Brautigam, Edwin Fischer, Emil Gilels, Friedrich Gulda, Clara Haskil, Jos van Immerseel, Julius Katchen, Wilhelm Kempff, Igor Levit, Mikhail Pletnev, Maurizio Pollini, Svjatoslav Richter, Arthur Rubinstein, András Schiff, Artur Schnabel, Mélodie Zhao
Beethoven: String Quartets — summary for comparisons of recordings, involving the following ensembles: Alban Berg Quartet, Amadeus Quartet, Artemis Quartet, Brooklyn Rider, Busch Quartett, Chiaroscuso Quartet, Emerson String Quartet, Endellion String Quartet, Guarneri String Quartet, Hagen Quartett, Kuijken Quartet, LaSalle Quartet, Leipziger Streichquartett, Melos Quartett Stuttgart, Quartetto Italiano, Quatuor Mosaïques, Takács Quartet
Beethoven: Violin Sonatas — Summary for comparisons of recordings, involving the artists Busch/Serkin, Capuçon/Braley, Faust/Melnikov, Grumiaux/Haskil, Kremer/Argerich, Menuhin/Kempff, Mullova/Bezuidenhout, Oistrakh/Oborin, Perlman/Argerich, Perlman/Ashkenazy, Szeryng/Rubinstein