Chopin Etudes - Murray Perahia
Mozart Sonatas - Mitsuko Uchida
Beethoven Sonatas - Daniel Barenboim
Good choices, except...the Beethoven. There are probably a million different opinions on this, but I think for the least idiosyncratic, and pianistically most compelling Beethoven Gilels is the winner, but unfortunately it's incomplete, the Op. 111 Sonata being the most obvious gap. IMO, there are many better complete sets than Barenboim. If you can put up with poor sound quality, Schnabel is of course the milestone against whom everyone is judged, particularly in the late sonatas. Kempff is perhaps the most consistent complete set, maybe the best for a beginning collector (which I assume you are) and always unimpeachable. I also like Goode, although I wouldn't recommend it as a first set. And I would absolutely avoid Brendel, whose set is IMO quite uneven. Of course, best is to own all of these

. The Beethoven sonatas are the absolute cornerstones of the piano reportoire, and has been satisfyingly recorded probably more than any other reportoire. Each great pianist brings to these works his own perspective and genius.