Not read most of these
I've only been reading for thirty years, so I haven't got around to all the recommendations on the listings here. So perhaps my own thoughts, older though they may be, can add some value.
All:
Arthur C. Clarke, Asimov, Heinlein, Phillip K. Dick, AE Van Vogt, EE Smith, Douglas Adam, Michael Moorcock, Terry Pratchett, Alan Dean Foster, Poul Anderson, CJ Cherryh, David Brin, Greg Bear, Larry Niven, Anne McCaffrey (especially for all the girls here), not forgetting H.G. Wells.
Dip into any of those to begin with, then work on the modern writers.