On my personal appreciation 'meter', Brahms strolls past the other composers in the group where I've listened to between 25 and 50 pieces (Haydn, Handel and Schubert).
Next-up, the rest of the mid-Romantic composers born 1834-1839 to include all of, "The Mighty Handful". I know I'm going to have a lot more time this week for listening and there's some beautiful music heading our way.
Level 1
Bizet, Georges:
Carmen
Level 2
Mussorgsky, Modest:
Pictures at an Exhibition
Rimsky-Korsakov, Nikolai:
Schéhérazade, Op. 35
Bruch, Max: Violin Concerto No. 1 in G Minor, Op. 26
Saint-Saëns, Camille:
Carnaval of Animals
Level 3
Saint-Saëns, Camille: Symphony No. 3 in C minor "Organ"
Delibes, Léo: Lakmé esp. Flower Duet
Mussorgsky, Modest:
Night on the Bald Mountain
Mussorgsky, Modest: Boris Godunov
Borodin, Alexander: Prinz Igor esp. Polovtsian Dances
Delibes, Léo: Coppéllia
Level 4
Borodin, Alexander:
String Quartet No.2 in D major esp. Notturno: Andante
Saint-Saëns, Camille:
Danse Macabre
Rimsky-Korsakov, Nikolai: Capriccio Espagnole
Bizet, Georges: L'Arlésienne Suite Nos. 1 & 2
Borodin, Alexander: Symphony No. 2
Bruch, Max: Kol Nidrei
Borodin, Alexander:
In the Steppes of Central Asia
Saint-Saëns, Camille: Samson and Delilah esp. Mon Couer S'Ouvre a Ta Voix
Bizet, Georges: Les Pecheurs de Perles esp. Au Fond du Temple Saint
Saint-Saëns, Camille: Piano Concerto No. 2 in G minor
Saint-Saëns, Camille: Introduction and Rondo Capriccioso
Mussorgsky, Modest: Songs and Dances of Death
Rimsky-Korsakov, Nikolai: The Tale of Tsar Saltan esp. The Flight Of The Bumble Bee
Level 5
Bruch, Max: Scottish Fantasy
Bizet, Georges: Symphony in C
Delibes, Léo: Sylvia esp. Pizzicati
Rimsky-Korsakov, Nikolai: Russian Easter Festival Chorus
Saint-Saëns, Camille: Cello Concerto No. 1
Saint-Saëns, Camille: Violin Concerto No. 3
Saint-Saëns, Camille: Piano Concerto No. 4
Bruch, Max: Symphony No. 3
Mussorgsky, Modest: Khovanshchina
Mussorgsky, Modest: Sunless
Level 6
Borodin, Alexander: Symphony No. 1
Saint-Saëns, Camille: Violin Sonata No. 1
Bizet, Georges: Jeux d'Enfants Suite
Rimsky-Korsakov, Nikolai: Sadko
Wieniawski, Henryk: Violin Concerto No. 2 Op. 22
Balakirev, Mily: Islamey
Rimsky-Korsakov, Nikolai: Symphony No. 2 "Antar"
Saint-Saëns, Camille: Havanaise
Waldteufel, Émile: "The Skaters' Waltz"
Balakirev, Mily : Tamara
Rimsky-Korsakov, Nikolai: Symphony No. 1
Saint-Saëns, Camille: Septet
Rimsky-Korsakov, Nikolai: The Invisible City of Kitezh Suite
Level 7
Saint-Saëns, Camille: Piano Concerto No. 5 "Egyptian"
Saint-Saëns, Camille: Clarinet Sonata in E-flat major, Op. 167 esp. I. Allegretto
Balakirev, Mily : Symphony No. 1
Saint-Saëns, Camille: Phaéton Op. 39
Saint-Saëns, Camille: Africa Fantasy
Paine, John Knowles: Symphony No. 1
Saint-Saëns, Camille: Le Rouet d'Omphale Op. 31
Smith, Alice Mary: Symphony in C minor esp. IV. Allegro Maestoso
Delibes, Léo: Les Filles de Cadix
Rimsky-Korsakov, Nikolai: Overture to May Night
Balakirev, Mily : Grande Fantaisie on Russian Folksongs
Saint-Saëns, Camille: Marche Héroique
Saint-Saëns, Camille: Basoon Sonata Op. 168
Reubke, Julius: Piano Sonata in B-Flat
Saint-Saëns, Camille: La Jeunesse d'Hercule Op.50
Honourable mentions:
Cui, César: Kaleidoscope esp. No. 9 Orientale
White Lafitte, José Silvestre: Violin Concerto in F-sharp Minor esp. ii. Adagio Ma Non Troppo
Goetz, Herman: Piano Concerto No. 1, No. 2 & Symphony in F Major
Rheinberger, Josef: Abendlied - Evening Song