Maybe I should have mentioned it: Beethoven, Haydn, Mozart, Bach, Schubert, Brahms, Schumann, Chopin, Dvorak, Handel, Bartok, Mahler, Mendelssohn....
Many of them have very good orchestral music, others very little or it is dwarved by their solo/chamber (Schumann, Schubert). My favorite mostly orchestral composers are probably Mahler, Bruckner and Wagner, but in general I am not the biggest fan of late romantic/early modern orchestral music (although of course there are some pieces I like a lot). And in some cases, such as Shostakovich I prefer the chamber music (but this might be a special case as his symphonies are very diverse and uneven, the concertos are mostly as consistently good as the chamber works).
Generally, I far more centered on composers than genres.