Of those on the list, I chose Richter, Gilels, and Kempff.
Possibilities not on the list: Solomon (he might be my number 1), Bruce Hungerford, Walter Gieseking, Robert Casadesus (only recorded a few)...
Richter, Solomon, and Kempff are probably my favorites. Richter mostly for the early live recordings I own (Op. 2/3 on Praga for example -- peerless), but his studio Op. 57 for RCA is also essentially peerless. He brings such life into anything he plays, and his technique is breathtaking. Never recorded a complete cycle.
Solomon plays Beethoven like an old sage in fine physical form. Every sonata he recorded is a winner. No pianist can nail the transitions as smoothly as Solomon could. He was a true genius regarding structure and phrasing -- and there is yet something so modest about his playing. Never recorded a complete cycle.
With Kempff, I only know the mono cycle. Yes, there are a couple duds. But they are few and far between, and a small price to pay for the poetic grace of Kempff. There is an earthy, human quality to his playing that sets him apart from any other pianist I've heard. Occasionally there is even a nervous feel to his playing, and somehow he gets away with it. Op. 26 Mvt. 4 is a case in point. Notice how he brings out the melody as it changes registers so delicately. I've never heard it played so slowly, and it changes my entire view on this piece.