Given your tastes, you’d probably love Ray Bradbury’s Martian Chronicles.
As far as Asimov goes, if you’ve read the Foundation series you’ve still got the Empire and Robot bunch to go. I remember Pebble in the Sky (Empire) and Caves of Steel (Robot) were some of his best long-form work, but the Robot short stories are where he really shines. I used to have The Complete Robot with every one of those – thing was about the size of a cinderblock, don’t know if you can get it anymore. One word of advice, don’t bother with Robots and Empire: he tried to tie everything together neatly and screwed it all up.
For the late, lamented Clarke, Rendezvous with Rama and Rama II are good, but stop there; 2001 and 2010 are great while 2061 is alright and 3001 was tripe (what was it with the old masters completely losing it as they aged?!); Childhood’s End was excellent.
And if you feel like reading something shamelessly pulpy, you could do a whole lot worse than Edgar Rice Burroughs’ Carter of Mars series.