The best fantasy series currently being published (because I say so, that’s why!) is George R.R. Martin’s “A Song of Ice and Fire.” It will be six books long when it’s completed; three are already out. The first is A Game of Thrones. His world is loosely based on England during the Wars of the Roses, and features literally dozens of speaking characters – but, remarkably, it’s not at all difficult to tell them apart or to remember their names. It’s an absolutely stunning achievement.
I’ll second the recommendation of Terry Pratchett – he’s funny and thought-provoking. His first few books are very jokey (and more specifically parodies than his later books became), so there are differences of opinion as to where to start. Some possibilities: The Colour of Magic (the first novel), Wyrd Sisters (the first really good one, which also introduces the small kingdom of Lancre and its witches), Small Gods (quite a bit later, but stands alone – much less humorous than most) and The Truth (very recent, also more or less stands alone, and shows Pratchett at his modern best).
Seconds also to Guy Gavriel Kay and Tim Powers (I particularly recommend his most recent novel, Declare, the secret magical history of the Cold War). Morrow’s really cool, too – Towing Jehovah is a powerful (and powerfully funny) book on many levels.
China Mieville has written an absolutely magnificent novel called Perdido Street Station that’s more fantasy than it is anything else. It’s set in a semi-industrial city (dirty and vibrant as London in Dickens’s day) and has an amazing array of characters, situations and activities. But it’s not for the faint of heart.
Neal Gaiman’s new novel American Gods is also very good – it’s one of the very few “Brit tries to explain all of American society and culture through fiction” pieces that I actually liked.
Steven Brust has a fast-paced and tongue in cheek series of novels about an assassin named Vlad Taltos – the first three novels are now available in an omnibus called The Book of Jhereg.
Sean Stewart has done some books I really loved (like Nobody’s Son – what happens after the low-born boy saves the kingdom and marries the princess – and Mockingbird – magical realism in Texas), and some that I found a tedious slog, like The Night Watch. Most of his books are very well-written at least; when he fails (in my opinion), it’s only through reaching too far.
Barry Hughart wrote three very funny novels set in mythic China, which were collected as The Chronicles of Master Li and Number Ten Ox. It’s out of print now, but may be findable; it’s well worth searching for.
And Sean Russell has written three two-book series that are fantasy mostly by courtesy (very little magic is done in them). The first was set in something like mythic China, and had great military maneuvering and tactics, and the other two had a world something like Georgian England, where magic was ebbing. His most recent book is a big epic fantasy in the George Martin mode, The One Kingdom, and it’s very good, too.
That’s probably too many already, so I’ll stop there.