TOD:
Almost impossible to answer.
But for early music, I can say that J.S. Bach is by far my single favorite. I was cleaning a few records the other day, to sample and decide if I still wanted to keep them. I put on Wanda Landowska playing the Well-Tempered books, thinking I might not return to this one, and with the early recording sound limitations and all, it wowed me, as invariably happens with most anything of Bach's. (I should add that one thing I love about this big album is the tipped-in signature of the ar-teest. It's a beauty.
As for the rest of classical music, only the grossest of generalizations could be made, and they'd be useless. Such as this one: I suppose I'm partial to the late-Romantic/early 20th century period. You know, the big fancy stuff. (How's that for gross?) But then there's Mozart. And Mendelssohn. Pure magic.