I've been a big fan of the subgenre dubbed "Sword & Planet" for a long time. However, as our knowledge of planetary science has grown, the genre has gradually obsoleted itself. The original Sword & Planet authors (long before the genre tag existed) like Edgar Rice Burroughs, Otis Adelbert Kline and Ralph Milne Farley were, of course, operating under the burden of a much more scanty body of knowledge about what the planets were like when they wrote in the Teens, Twenties and Thirties. Their characters' adventures on Mars and Venus were, as far as anyone knew, scientifically plausible at the time. In fact, with the prevalence of Percival Lloyd's Martian canal obsession, they may well have been fueled by scientific understanding of the time.
When they came back into print in the 1960s, that was no longer the case. However, a new generation of writers cropped up who imitated the genre conventions (and this is where the genre tag was coined by Don Wollheim (of DAW books fame) and they had to contend with the fact that our understanding of planetary science had made the entire genre impossible, and therefore not within the realm of science fiction, even remotely.
There were two approaches to it that seem common at that time. Guys like Lin Carter with his Jandar of Callisto series and Mike Resnick with his Ganymede series, just ignored it, made some vague claim at the beginning of the novel that the protagonist realised that science said his story was impossible, but that it was true nonetheless! This was a bit of a wink and a nudge at the readers, though, and other series did things differently. Lin Carter's Green Star series (as well as many other series, such as F. Gardner Fox's Llarn series, Kenneth Bulmer's Dray Prescott series, and L. Sprague de Camp's Krishna series) set their stories outside of the solar system where nobody could argue with the idea of human aliens living on worlds that we knew to be inhospitable to human life.
Most recently, a handful of neo-Sword & Planet books have popped up. In particular I'm thinking of S. M. Stirling's series set on Venus and Mars that are alternate history; the Russian Venera probe operated about as long as it really did, but instead of being destroyed by the hostile environment, it was clubbed by a caveman.
You know what I'd like to see? A far-distant future that sees the planets of our solar system terraformed, to a certain extent, and then society falling backwards to a pre-space traveling technological age, stranding human colonists for generations until they become natives of their planets. Either that, or some other pseudo-scientific explanation that includes the possibilities of human-like life on the frozen worlds beyond the asteroid belt. I like fantasy as much as the next guy (probably a good deal more, actually) but I even more like to integrate as much plausibility, reality and SCIENCE as possible. I guess I'm an old school "Weird Tales" fan when you get right down to it. Back in the day before science fiction and fantasy parted ways in the minds of most audiences and became two completely different things.