Last week Ender's Game was knocked out by The Hitchhiker's Guide to the Galaxy. The competition was closer than I expected. Well, 2 to 1 isn't really close, but I honestly expected a slaughter.
This week we have a faceoff between two great masters. Though I suspect Herbert gets that title on the strength of this one book alone. I have enjoyed some of his other work - The Dosadi Experiment and Whipping Star I recall as being quite good for example. But I've read other of his works that were less than stellar. And of course fans argue endlessly about the merits of Dune's various sequels.
Asimov on the other hand has a huge and very impacting bibliography. He's best known for the linked stories of Foundation and his Robotics tales, but he also gave us stories like "Nightfall" (as run in Escape Pod 100), The Bicentennial Man, The Gods Themselves, and many nonfiction works on science. If you're asked to think of an iconic Science Fiction author, chances are you think of Asimov.