When I read your comment I'm strongly reminded of myself ten years ago. I held almost exactly the same view on hard scifi, and was similarly obsessed with Arthur C Clarke. But I've since loosened my definition of scifi for a couple of reasons:
a) I now think of scifi as any work intended to do more than tell a story or explore a world. Focussing on just hard scifi causes great works of social and sociology fiction like The Dispossessed to be left without a clear pigeonhole. Which is a great pity, IMO.
Perhaps the biggest chunk that gets miscategorized is cyberpunk; works like Snow Crash and Hardwired are clearly about more than whether the ending is happy or sad, or whether the hero gets the girl. Doesn't seem right to categorize them as fantasy. Better to narrow Arthur C Clarke into the sub-category of hard scifi. Loosening my uptight definition caused me to better appreciate Snow Crash in particular on a second reading a decade later. It's aged wonderfully.
You could even imagine a book with fantasy 'props' that feels scifi-like. I haven't seen it yet, but I have no doubt it can be done. (Any recommendations from others?)
b) Not even everything Arthur C Clarke wrote was hard. Rama series, c'mon! Kim Stanley Robinson is a great author, but I fail to see how he's 'more hard' than Asimov or Heinlein. Somebody described the Red Mars series to me as a reality show with dune buggies, and that seems about right. You certainly couldn't call it 'more hard' than Anathem.
Anyways, for hard scifi readers the top author today is probably Greg Egan. That I think everybody can agree on. I have other recommendations elsewhere on this thread.