I was "relieved" to see that I've read like 25 of the "top 100 according to random guy". And several more are books I already own, sitting on the nightstand waiting for me to have time...
Glad to see some of my hard-SF favorites on the list, such as Joe Haldeman's excellent Forever War as well as the Cyberpunk's bible Neuromancer by William Gibson. Also refreshing to see a sense of humor in the list creator as Douglas Adams' The Hitchhiker's Guide to the Galaxy is one of my all time favorite works of humor, loosely SF as it may be.
However any list like this is bound to generate the requisite list of "Stuff I thought Should Have Been on the List", so here are my entries for overlooked great SF:
- Oath of Fealty - Larry Niven and Jerry Pournelle
- The Cat Who Walks Through Walls - Robert A. Heinlein
- Steel Beach - John Varley
- Heir to the Empire, Dark Force Rising, & The Last Command - The Star Wars: "Thrawn Trilogy" - Timoth Zahn
- The Hammer of God - Arthur C. Clarke
- Everything by William Gibson that wasn't on the list, except possibly The Difference Engine, co-written with Bruce Sterling
- The remainder of the "Increasingly Inacurrately Named Hitchhiker's Trilogy" (in 5 books) from Douglas Adams.
Just a few suggestions... Some are more of an investment. Others, like the Heinlein stuff, can be read in a solid day spent on the beach or out of the rain.