What did I treasure when I was younger... C. S. Lewis? Hmm. Well his fiction is as well written today as it ever was. Anne MacAffrey? Well, her earliest writing is far better and edgier than the later stuff, but that's a different problem. David Eddings? No, his writing is still good. Clifford Simak? *shrug* He's still great.
Never read any Heinlein, though. Somehow avoided him. Read a little Asimov and Clarke; my brother liked them better. Pournelle and Niven I discovered more recently.
Wade.