[Erax]

I started reading SF pretty much in the order it was written. I began with Jules Verne as a kid, then moved on to H.G. Wells. From there I was ready to tackle my dad's SF collection, which had quite a bit of Asimov, Clarke, Heinlein and Bradbury, along with other authors. I'd go through a 'Niven phase', then a 'Philip K. Dick phase', and so on. I don't read as much SF these days, but I read a LOT of it as a teenager.
Clarke is my all-time favorite SF author.

My fantasy collection began with Tolkien, which I read at 11. I'd say it spoiled me - for years I couldn't find anything to compare with his work, but finally I found the Dying Earth series by Jack Vance and 'Magician' by Raymon E. Feist.

I also went through a 'Lovecraft phase' a few years back and I recommend anything by him or by Robert Bloch.

I started reading Terry Pratchett (he's in a Category all by himself) in 1988 and haven't stopped since.

My wife is a big Stephen King fan and I've read some of his books. Not one of my favorite authors but he's got great characters and gives me a good window into American culture. His 'On Writing' (nonfiction) is good reading if you intend to become a writer.