Bach, Mozart, Beethoven...need I say more?
Very difficult. Currently enjoying Pergolesi's Stabat Mater, also love Faure's Requiem, but wouldn't rate either as consistently great composers.
Beethoven's Emperor Piano concerto mvt 2 and 'Shepherds give thanks' from his 6th symphony are ethereal. But Bach's 'jesu, son of man's desiring' is heaven elevator music, as is 'Liebster Gott' and so many others. And Mozart is just...perfection. Watch Amadeus.