Hm, the majority of my favorites come from the 20th century, so I am not sure if Evelyn Waugh, G.K. Chesterton, C.S. Lewis, Jorge Luis Borges, Frederich Buechner, Shusaku Endo, Graham Greene or the like qualify.
Out of the older stuff, it is hard to dislike the epics poems. Milton's
Paradise Lost is an easy pick. So is Alighieri's
Divine Comedy, but the cultural gap is larger, making it more difficult for me to truly appreciate it.
Out of the plays, Shakespeare's tragedies, particularly Hamlet, strike my fancy. The Greeks have a lot of great stories as well, although my memories of them are hazy enough that I don't dare pick a favorite --outside of giving a special tip of the hat to Euripides and his gritty portrayals.
In the realm of non-fiction, there are many great philosophical works. I, unfortunately, haven't read many of them to completion, but S. Kierkegaard always gets an honored mention. The theologians are fascinating reads as well. Virtually every major religious writing falls under your description of a "Classic", so I won't even try to list them all.
As for Novels, there is
Notes from Underground by Dostoevsky. As well as the works of Mark Twain and H.G. Wells (especially
The Island of Dr. Moreau, which is closer to horror than science fiction). Oddly enough, I don't think I have read many novels written prior to the 1900's.
Short fiction has great representatives in Arthur Conan Doyle, H.P. Lovecraft, and Edgar Allen Poe. The mystery, science fiction, and horror genres have much to owe to them, while I owe them many a fine evening's enjoyment.
For Poetry, you will have to talk to someone else, I am afraid.
I consider it my life goal to finish reading Les Misérables before I'm 30. XD I'm about 1/5 of the way there! It's an excellent story, and a fascinating read so far.
Ah, that is a truly tough novel. I just started it a month ago, intending on marathoning my way through in a few weeks, but work and Hugo's darn writing style got in the way. I am only a small way into the recounting of the Battle of Waterloo, at the moment.
I like the story well enough, but considering the way he writes I can only conclude that he was paid by the word. As I go through the novel, he will set up these beautiful scenes, and write in glorious prose. He will capture the essence of a mood or thought perfectly through some indirect method (such as the image of Jean Valjean pacing in his room, trying to decide whether to turn himself in and give up his position as mayor, as told from the servant's point of view), and I will say to myself "now
that is why this is a classic". Then he will spend the next fifty pages recounting (and trampling all over) the same scene in the most dry manner possible.
You know all of those tricks you learn during NaNoWriMo to boost your word count? You know, making huge lists that add nothing to the story, going off on tangents about whatever enters your mind (even if they aren't related to the story), retelling the same encounter from a bunch of different perspectives, and all that? Victor Hugo new all of those tricks too, and he applies them liberally.
Frankly, I am still trying to decide whether it is worth finishing or not. I could be reading so many other, more efficient books right now.