Ahhhh, One of my most favorite subjects!!
My favorite genre so far is fantasy/sci-fi. I know those aren't the same thing, but as far as being likely they are pretty much equal in most cases. That's why I group them together.
My favorite sci-fi author is, and probably always will be, Robert A. Heinlein. Soap-Opera Science Fiction, as my mom likes to call it. He was a wonderful writer.
As for the fantasy genre, well, there are so many that I've read that its hard to narrow down to favorites.
Mercedes Lackey has written many books. There is a set called Bardic Voices, and one called The Last Herald Mage, and Mage Wars. She has written with Larry Dixon, and Piers Anthony (another fav). She's quite wonderful.
David Eddings wrote The Belgariad, and The Mallorean and a few others similar. I would recommend his books because of the wonderful characters in them. Every time I read them I crack up at Silk's little witicisms and Polgara's biting sense of humor.
I mentioned Piers Anthony above, too. He is deffinately worthy of notice. I loved his entire Xanth series, although they consisted of only bad puns. It increased my brain activity to try to figure out all of the hidden puns in each story. Good reads. Anthony is also, in my opinion, a very noted sci-fi writer, too.
These are my favs. Who are yours?
I'd have to say that Mercedes Lackey is probably #1 fav, so far. David Eddings is right up there with Lackey.