Asimov is excellent. Here is my top shelf A to C Not showing off I hope, it's just interesting.
I read Foundation series early on due to my quest to read every Hugo winner. However I also read iRobot and The Gods Themselves. I haven't read the Robots sequence but I will reinvestigate Asimov.
My List
Douglas Adams - naturally!
Brian Aldiss - Hothouse was good, although more dystopian than Sci Fi. Non Stop was also good but his stuff is early and I got into Space Opera.
Poul Anderson - Tau Zero was a hard sci fi concept book that I really loved. quite dark really.
Asimov - as stated - The Foundation series is truly a must read.
JG Ballard - not really a Sci Fi Writer but this is good. Human relationships and odd throughout.
Iain M Banks - As you can see I did really like him but it is easy reading compared to some more challenging Sci Fi. Good for travelling!
Greg Bear - Really liked all these books and had a "bear" phase. Eon is the best, followed by blood music I think.
Gregory Benford - Forgot this one!
Alfred Bester - GET ALL HIS BOOKS, I NEED TO READ MORE
Ray Bradbury - Just a classic book I think deserves to sit here.
Orson Scott Card - Meh
Michael Chabon - not really a Sci Fi book - more alternate history. I quite enjoyed this but wouldn't rush to recommend it in this context. Kavalier & Clay by him is MUCH better.
Another shelf soon - CASSIE MADE ME SPEND MONEY ON THIS.