BEST brand for Classical Recordings?

+1 on Philips and Decca. Those recordings are gorgeous. The box sets, if still available, are great value! L'Oiseau-Lyre (Decca) and Erato and Argo are also phenomenal. 

Harmonia Mundi (U.S. and French), for both music and sound.

Astree and Lyrita and Nonesuch. Super duper! 

Really just one, I don't know that I can. My favorites for CD have been;
Harmonia Mundi, ECM, Pentatone, moderntimes_1800, Zig Zag, cpo and BIS.

For remastered vintage recordings;
Orfeo d'Or, Andante.

My favorites for original monophonic vinyl have been;
Archiv Produktion (DG), London/DECCA and Haydn Society Records.

I've enjoyed DB, Decca, Pentatone and Sony recordings, have a very nice SACD setup, enjoy most (but not all) of those recordings.

I have been very pleasantly surprised by Naxos recordings, all "regular" CDs, usually not performed by "household" names, but the quality of the recordings and performances are outstanding.

I really enjoyed their " Naxos 30th Anniversary Special Edition Box Set", great selection, very nicely recorded and performed, excellent value!