Here's a collection which I could survive on:
Machaut: Mirror of Narcissus (Gothic Voices), Motets (Ensemble Musica Nova), Messe de Nostre Dame (Ensemble Gilles Binchois)
Dufay: Sacred Music from Bologna Q15 (Clerks' Group), Missa Se la face ay pale (Diabolus in Musica)
Ockeghem: Missa de plus en plus - chansons (Orlando Consort), Requiem (Ensemble Organum)
Josquin: Missa Pange Lingua (Ensemble Clement Janequin), Motets (Orlando Consort)
Byrd: Masses (Tallis Scholars), Keyboard Music (Moroney)
Lassus: Lagrime di San Pietro (Herreweghe)
Monteverdi: Madrigali Guerrieri et Amorosi (Concerto Italiano)
Biber: Rosenkranz-Sonaten (Goebel)
Purcell: Dido and Aeneas (Hogwood), The Fairy Queen (Christie), King Arthur (Christie)
Rameau: Hippolyte et Aricie (Christie)
Handel: Messiah (Dunedin Consort), Acis & Galatea (Dunedin Consort), Alcina (Curtis), Giulio Cesare (Jacobs or Minkowski), Ariodante (Minkowski), Water Music (Savall)
Francois Couperin: (Hantai), (Scott Ross)
Scarlatti: (Scott Ross), (Hantai), (Pogorelich)
Bach: Brandenburg Concertos, Orchestral Suites, and Chamber Music (Musica Antiqua Koln), Goldberg Variations (Hantai I and Gould I), WTC (Gilbert and Koroliov), Partitas (Gilbert or Leonhardt and Xiao-Mei), Violin Sonatas & Partitas (Kuijken I or Mullova), Cello Suites (Bylsma I), Matthew Passion (Herreweghe I or Leonhardt), Cantatas (Leonhardt/Harnoncourt, Herreweghe, Gardiner, Suzuki), Organ Works (Rubsam, Alain, Foccroulle, or Vernet)
C.P.E Bach: (Spanyi, Keyboard Concertos vols 13, 14 & 15), Symphonies and Cello Concerto (English Concert)
Haydn: Quartets (Quatuor Mosaiques), Paris Symphonies (Harnoncourt), Sturm und Drang and London Symphonies (Bruggen and Harnoncourt), The Creation (Hogwood or McCreesh), The Seasons (Jacobs), Piano Sonatas (Brautigam or Schornsheim)
Mozart: Piano Concertos (Bilson and Gardiner), Da Ponte Operas (Jacobs), Magic Flute (Ostman or we'll see new Jacobs), Symphonies (Mackerras on Linn), Requiem (Harnoncourt), Mass in C Minor (Gardiner or Herreweghe), Piano Sonatas (Brautigam and Gulda), Night Music (Manze), Quartets (Quatuor Mosaiques), Quintets (Quatuor Talich)
Beethoven: Symphonies (Harnoncourt and Mackerras/Edinburgh, 6th Walter, 9th Fricsay and Lucerne Furtwangler), Sonatas (Schnabel, Gulda, Serkin, mono Kempff, Pollini and Richter late, Brautigam), Diabelli Variations (Schnabel or Serkin), String Quartets (Takacs and Talich), Cello Sonatas (Schnabel/Fournier), Violin Sonatas (Faust/Melnikov), Archduke Trio (Cortot/Thibaud/Casals), Piano Concertos (Schnabel/Sargent, Fleisher/Szell, Kempff/Kempen, and Lubin/Hogwood, Gilels/Ludwig 4, Moravec/Turnovsky 4), Missa solemnis (Klemperer and Herreweghe)
Schubert: Winterreise (Fishcer-Dieskau, Quasthoff), Die Schone Mullerin (Fischer-Dieskau, Gura), Late Sonatas, Musicaux etc (Schnabel, Richter, and Staier), String Quartets (Takacs), Trios (Cortot/Thibaud/Casals and Stern/Istomin/Rose; or Florestan Trio), Symphonies (Harnoncourt), Quintet (Casals)
Chopin: Nocturnes (Moravec), Preludes (Cortot), Ballades (Cortot), Etudes (Pollini), Scherzi (Pogorelich or Moravec), Waltzes (Cortot or Lipatti), Mazurkas (Sofronitsky or Kapell), Sonata 2 (Rachmaninov), Sonata 3 (Argerich)
Schumann: Kreisleriana, Davidsbundlertanze, Dichterliebe (Cortot), Symphonic Etudes (Richter or Pollini or Cortot), Kinderszenen (Cortot or Moravec), Carnaval (Rachmaninov or Michelangeli '57), Toccata (Pogorelich), Concerto (Richter or Moravec), Quintet (Serkin/Budapest)
Liszt: Sonata (Levy perhaps), Transcendental Etudes (Arrau or Berman), Concertos (Richter), Richter in the 1950s 3
Wagner: Tristan and Isolde (Furtwangler), Walkure (Keilberth or Krauss)
Brahms: Symphonies (Klemperer, Walter/Columbia 2-3, Giulini LAPO 1 and 2, Kertesz, Kleiber 4), Serenades (Mackerras or Kertesz) Piano Music (Katchen), Ballades (Michelangeli or Gilels), Piano Concertos (Fleisher/Szell, Freire/Chailly), String Quintets (Leipziger Streichquartett), Trios (Stern/Rose/Istomin or Florestan Trio), Piano Quintet (Staier/Leipziger, Tackas/Hough), Piano Quartets (Gilels/Amadeus), Cello Sonatas (Immerseel/Hough or Serkin/Rostropovich)
Bruckner: Symphonies (set Jochum DG, Giulini 8 & 9)
Verdi: La traviata (Callas), Falstaff (Karajan), Requiem (Giulini)
Dvorak 7-9 Harnoncourt, 8-9 Kubelik, 9 Ancerl and 8 & 9 Talich, Slavonic Dances (Harnoncourt or Kubelik), Quartets (American, etc, Janacek Quartet or Panocha Quartet)
Scriabin: Sofronitsky (Denon)
Janacek: Piano Music (Firkusny), Cunning Little Vixen and From the House of the Dead (Mackerras), Taras Bulba, Glagolitic Mass, Sinfonietta (Mackerras and Ancerl)
Debussy: La Mer/Nocturnes, and Images/Prélude à l'après-midi d'un faune (Boulez/Cleveland), Preludes I and Images (Michelangeli), Complete Piano Works (Bavouzet), Pelleas et Melisande (Desormiere)
Ravel:Daphnis et Chloe (Boulez or Munch), Bolero (Boulez), Concerto in G (Michelangeli), Piano Works (Bavouzet), Gaspard (Michelangeli BBC and Pogorelich), Trio (Trio Dali)
Mahler: Symphonies (impossible to list but some options): 1 Kubelik (Audite) 2 Walter or Klemperer 3 Kubelik (Audite) or Bernstein (NYPO) or Gielen 4 Walter, Kubelik (DG) or Kletzki 5 Walter or Barshai 6 Mitropoulos (WDR) or Bernstein (NYPO) or Boulez 7 Kubelik (Audite) or Gielen 8 Kubelik (Audite) 9 Walter or Ancerl
Rachmaninov: Richter (Regis)
Stravinsky: Petrouchka (Monteux/Boston), Le Sacre (Markevitch), or Stravinsky for both, Symphony of Psalms (Ancerl or Stravinsky), Les Noces (Ancerl)
Schoenberg: Verklarte Nacht (Hollywood Quartet), Quartets (Juilliard mono), Piano Music (Pollini or Paul Jacobs), Serenade and 5 Pieces for Orchestra (Boulez, BBC), Pierrot Lunaire (Boulez and Schafer)
Box sets, because they are great:
Berg: Alban Berg Collection (DG)
Webern Complete Webern (DG)
Bartok: Quartets (Juilliard '63 or Vegh stereo), Concerto for Orchestra (Reiner), Piano Concertos (Anda or Kocsis), Mikrokosmos/Piano Music (Kocsis), Bluebeard's Castle (Kertesz)
Ligeti Ligeti Project I-IV, Ligeti Edition 1-3, 4 - or the two main Wergo cds with Lux Aeterna and Requiem