That's a weird dichotomy, since Science Fiction can be both realistic or not. I guess it must be because in computer games, Science Fiction for the most part is just a regurgitated mish-mash of cliches from other computer games rather than a setting that tries to make sense.

The dichotomy you should have used was realistic or fantastic. You could also have asked if people prefer their post-apocalyptic games to be futuristic, contemporary, historical or pre-historical. As to your original question I like both approaches but at the same time I really hope that more Science Fiction computer games would try to be realistic. Most Science Fiction games are severely lacking in both realism as well as imagination. But since most computer games are made by people that seldom read neither fact or fiction, I'm sure I will be left wanting.

I can say with certainty that you are wrong. That which restricts the creativity among computer game developers is not adherence to realism. There are other causes for that. Working within a set of confines can be very good for our creativity.

If adherence to realism were the main obstacle to creativity, fantasy games should be the most creative genre. But by far, they are not. For every game like Sacrifice there is a ton of games with the same orcs, dwarves and elves. (I love Tolkien's works, and some computer games like Age of Wonders have put their inspiration to good use but you can't find a genre with a more ironic name than fantasy.)

Certainly but why would someone target something else than cities and strategical targets. Or would you fire a nuclear weapon right into an unsettled area where no military target is located?
And wastelands would be most certainly so high in radiation that nothing could survive there for long.

I prefer Sci-Fi, realistic is too much of a downer. I like it when a game takes you someplace you could only imagine before.

I don't know, I've seen "science fiction" which has stretched the "science" part to breaking point. I've also seen science fiction which has more or less become science fact over time. That said, though, I do agree, and it rather saddens me. That's why I tend to like settings like Ars Magica's, or Darklands' (though I admit I haven't played much of either for other reasons). While they also take from a different setting rather than inventing new things of their own, that setting is the surprisingly underused "real" medieval times, as the people of the time saw themselves.

EDIT: Oh, yes, the thread was about post- apocalyptic settings. I'm not sure whether I'm really that concerned about the matter: provided it's not too advanced it's simply a question of "was the disaster this century or the next one?" If I had to pick a favourite post apocalyptic setting, I'd go for that of the Mortal Engines series. What's interesting is that though there are elements of technology rather beyond what we have today, especially on the weapons front for obvious reasons, they aren't very prevalent in the overall plot. Many of the things which the people in the setting consider incredible are everyday items for us: tin foil being an amusing example due to its impossible thiness. The "old-tech" is something which the characters can use and experiment with, but do not truly understand, and treat in many ways like magic. Indeed, due to that fact I'd consider Mortal Engines an unconventional form of fantasy: if they understood more of how the old technology worked and there was less of an aura of mystery surrounding it, I wouldn't consider it fantasy at all. That, I think, is the key feature of a post apocalyptic setting I'll enjoy: not whether the ancient items exist yet in reality, but whether the knowledge of their workings has been preserved within the setting.

I think the difference is like that between Star Trek and Star Wars. Star Trek (I've heard: I haven't watched much of it) justifies many of its events with on real scientific theories; Star Wars includes many things which are scientifically wrong or implausible for the sake of a good story (and I'm not merely referring to Han's infamous "9 pasecs" comment).

...Oh, read the tv tropes article on it.

I can play either, but I prefer the mutants and fantastical stuff thrown in there. If it's a good enough story it doesn't have to have those things in it. I probably liked the Road more than Denzel's Book of Eli, but I enjoyed both of them.
Actually, the only fantasy setting I can't stand is the superhero world. I know it's blasphemy, but I don't want to watch another X-Men or Fantastic Four movie as long as I live.

I remember wikipedia listed a long list of sub-genres of science-fiction literature...
Maybe game devvers could read that and just pick one that's not never used before.

Btw. I remember Einstein said something on the lines:
"I don't know how the WW3 is going to be fought, but WW4 is going to be fought with sticks and stones."

Hey, how is Star Wars unrealistic? All you need is fusion power! It explains everything (or not) :D
Just joking... Lovely topic!

I prefer post-apocalyptic realistic sci-fi zombies.

Science Fiction can be more or less realistic just as contemporary or historic fiction can be. For example, contemporary fiction may be more or less realistic depending on the thoughts, dialogues and actions of the characters in that fiction. The amount of events with a low probability of happening that happens through the narrative would be another way to measure realism. Science Fiction however is by it's nature less realistic but not unrealistic. It is by it's definition not just "make believe" set somewhere in the future as that would be fantasy (and fantasy can be more or less realistic as well).
In addition to all measures of realism in contemporary fiction, Science Fiction which is set in the future must be measured by other criteria as well. How realistic is the technological changes in the fictional world compared to what we know today (which probably is different from what we knew when it was written). How realistic is the changes in human society compared with what we know today? And how realistic is the changes to the earth or universe compared with what we know today?

Science Fiction, although speculative can be very realistic, that is to say that what happens does not seem improbable (from what we know today). That does not mean that the exact events happening in any fictitious work that takes place in the future is very likely to happen. Predictions of the future usually are wrong and the more predictions you make, the more likely you are to fail.
I like the zombies in Ghouls'n Ghosts. However, they always get me in the end. But as they say, losing is fun :)