A few more suggestions, now that I've had time to gather my thoughts a bit.
The Dresden Files - Urban fantasy series by Jim Butcher, up to more than 10 novels and he writes them fairly quickly, at least once a year. The first novel is Storm Front. The series has a film noir tone, and its about Harry Dresden, private investigator and Chicago's only real live listed Wizard. Butcher's writing style definitely isn't the best in this list, and some of you more literary types might cringe at the overall quality, but his characters are interesting, his world is fascinating, and his pacing keeps you hooked very similar to the way in which Rowling is capable of.
The Silmarillion - more a history book than a fantasy novel, the post-mortem companion piece to Tolkien's the Lord of the Rings. This book is NOT for everyone. If you hated history in school, maybe not up your alley. Its dense, and very dry in most places. But if you can get past all that, the world Tolkien created is on par with none. He truly was the grandfather of world building.
The Dark Elf Trilogy - The first novel in the series is Homeland, I believe. A bit sophomoric. Salvatore isn't going to be winning any Pulitzer's anytime soon. But the character of Drizzt Do'Urden, while arguably damaging to the preteen fantasy community, has captured so many people's imagination for a reason. His fight scenes are also extremely complex and elaborate, take that as a pro or con as you will.
The Picture of Dorian Grey - I think this one qualifies as fantasy, right? Or maybe science fiction? Anyway, Oscar Wilde at his best. The rest speaks for itself.
The Divine Comedy - Italy's great epic, Dante Alighieri has done so much to shape our conception of the afterlife that the average first-world citizen often can't tell the difference between the Biblical myths and Dante's. Obviously, its a 14th century poetic epic, so not exactly super accessible. Also, be forewarned that more than anything, the DC was just as much a tool for political commentary than anything else, so most of the time Dante is shit talking politicians we've never heard of and don't understand the relevance for. But if you can find a simplified translation or wrack your brain over the original poetry, there's all sorts of juice in there. Inferno is obviously the most popular, Purgatorio And Paradisio are hit and miss.
Paradise Lost - 17th century England's answer to Dante, pretty much any misconceptions we have about God and Biblical myth that weren't established by Dante are the fault of John Milton. Perhaps one of the last great epic poems so far in history, although Milton's epic is only slightly more accessible than Dante's, the story that he weaves about God and Lucifer, angels and men, has shaped the spiritual consciousness of the Western world for centuries.
That's it for now. I'm sure I can think of more.