First and it's not even close : Iain M Banks (read them in publication order), if you haven't been there, wow what a treat you have in store.
Classics you might have missed : William Gibson , the first 6 Dune books (4 is a bit of a slog but 5 and 6 are a bit better). The Neverness/Requiem for Homo Sapiens Saga by David Zindell. The Hyperion saga.
More recently : Peter F Hamilton has written well over a dozen absolute doorstops. (start with Pandora's Star and Judas Unchained, if you like those there are plenty more).
Lesser known but I personally really enjoyed them : Dan Worth's 6 book Dominion saga. Miles Cameron Artifact Space and Deep Black.
Others from my recent years that I rather enjoyed. Loads of things Cory Doctorow, try Makers first (which should be free), next maybe Walkaway. Chuck Wendig's Wanderers and Wayward.
The Girl with All the Gifts (was made into a film), and sequel The Boy on the Bridge