Here are the Hugo Award winners for novels.
http://en.wikipedia.org/wiki/Hugo_Award_for_Best_Novel
We've pretty much covered the list. The good thing about sci-fi is that you can go back as far as the early 70's and the novels are still not really dated. You can read the best sci-fi novels for 1970 and they could for the most part have been written last year. That's not quite so true for post-apocalyptic and definitely not true for mysteries.