My primary focus is on classical music, so that's what I'll focus on in answering your request. In my experience, you can rarely go wrong with the sound quality and musical aesthetic from the following record labels. It's well worthwhile to explore their catalogues.
..Decca (any of the Speakers Corner reissues)
..EMI (avoid Angel LPs)
..Mercury (the Speakers Corner reissues are superb)
..Nonesuch (especially Aubort/Nickrenz productions)
Recording engineers who almost always deliver outstanding sound quality, and whose recordings I will buy without hesitation, include:
..Mark Aubort (Nonesuch and others)
..Bob Auger (CRD, ASV, Hyperion and others)
..Tony Faulkner (Decca, Hyperion and others)
..Antony Howell (Hyperion and others)
..Peter McGrath (Audifon, Harmonia Mundi)
..Jean-Francois Pontefract (Harmonia Mundi)
..Kenneth Wilkinson (Decca, Lyrita)
As to some specific recommendations of excellent performances in superb sound, I'll offer the following random recommendations for you to consider:
~ Vivaldi, Flute Concertos, McGegan/PhilBarO/J.See, Harmonia Mundi HMC 5193
~ Mozart, Horn Concertos, McGegan/PhilBarO/Greer, Harmonia Mundi HMU 7012
~ Stravinsky, Firebird, Dorati/LSO, Mercury SR 90226 (Classic Records reissue)*
~ Sibelius, Sym 2, Barbirolli/RPO, Chesky CR3
~ Berlioz, Symphonie Fantastique, Freccia/RPO, Chesky CR1 (one of the great symphonic recordings, and greatly overlooked)
~ Rachmaninov, Piano Concerto 3, Dorati/B.Janos, Mercury SR 90283 (Speakers Corner reissue)*
~ Respighi, Ancient Airs and Dances, Dorati/PhilHung, Mercury (the Golden Imports pressing sounds just fine)
~ Holst, The Planets, Previn/LSO, EMI ASD 3002
~ Charpentier, Te Deum, Christie/Les Arts Florissants, Harmonia Mundi
~ Prokofiev, Scythian Suite, Dorati/LSO, Mercury Classic Records reissue)*
~ Mendelssohn, Sym 3 (Scottish)/Hebrides Overture (Fingal's Cave), Maag/LSO, Decca SXL 2246 - 45 (Speakers Corner reissue)*
...* Currently available new; the others you'll have to find used.
Also, for an extended listing of recommended LPs based on sound quality, I agree almost point for point with Aurthur Salvatore's "Supreme Records" list. This list matched my record collection to a very high degree and I think he hits the mark consistently with his recommendations: http://www.high-endaudio.com/index_ac.html
For Jazz, look at the reissues coming from Analogue Productions, Speakers Corner and Classic Records.
Sidssp has presented a good list of recordings; I concur with his recommendations as well.
Good luck in your explorations.