What I've always liked about Clarke's work...
...is the believabilty of his novels. They all seem to be based on solid scientific principles. With fantasy I can accept the totally wild and bizarre, however with sci-fi there must be a strong element of 'this could actually happen' running through his books.
Clarke I think was called somewhere a modern day prophet for his accuracy in predicting the creation of satellites, and I think in 'Imperial Earth' I recollect him mentioning a device very similar to our current tablet computers.
My favourite Clarke novels would have to be '2001-A Space Odyssey' and 'Rendezvous with Rama', although I do enjoy reading his short stories.