Say it with me. Exposition about technology does not equal hard sci-fi. Ringworld and Foundation would both qualify as hard sci-fi, albeit the soft sci-fi of the spectrum, since they deal less with technology (the Ringworld in Ringworld and a few gadgets come to mind) and more with psychology, societal development, and evolutionary concepts.
By their nature, the split between hard and soft in video game sci-fi is a much more generalized one. On the one hand, you have games like Advent Rising, which is a big old space operaey Star Warsian style drama. Very very soft, if deserving of a hardness rating at all. The Halo series, on the other hand, draws a lot of hard from the Halos themselves, the concept of the Flood as a plague species, and the technological disparity of the Covenant and Human forces. Again, not as hard as sci-fi, because it's a video game, but definitely what I'd call a hard sci-fi story.
As a side note, Bioshock disguises magic as genetics, and asks you to believe in a city built under the ocean. I can't say as I see any hardness there, although I'd buy it if we were going to talk about the devolution of the splicer's minds.
Bioshock does try to state one philosophical talking point, it just doesn't deliver much of anything with it. By comparison, Halo really only offers one element like that, and that's the idea of the singular messianic hero. It was Master Chief in Halo 1, the Arbiter in Halo 2, and if the Believe campaign is even close to right, it'll be Master Chief again in Halo 3.
We criticize games for sending you on lengthy fetch quests to advance to the next point in plot when I think we should be criticizing them for little more than lengthy fetch quest to begin with.