1) Bradbury. He's just about the last of the great old ones, and he's been one of my favorites since childhood.

2) Gaiman. He's the obvious heir to Bradbury in style and tone, and probably my current favorite author overall, with presumably lots of writing still ahead of him.

3) Um... Card's certainly a thought. Maybe Stephenson - Snow Crash makes my all-time top five, and Diamond Age and Cryptonomicon were both excellent as well, but the newer stuff isn't as impressive.