I believe the film you are talking about is Solaris, which I believe is based on very well regarded russian Sci-fi (Stanislaw Lem?)...
Its an interesting case, actually. The science is fairly hard, with regard to the interstellar travel (I guess. I mean part of the point is that they are sort of stuck out there because easy, fast FTL isn't an option... I've never seen it. I have better ways to take naps.), so the issue is the planet, which is clearly psychic (is it the planet or a planet covering life form? One being sentient is Hard, the other is obviously far more speculative. THe relatively hardness of psychic stuff is debatable, I suppose), while the entire point of the story, and the reason it is well regarded (again: Never seen/read it) is to reflect humanity back on itself by showing us ourselves... in this case George Clooney and his survivors guilt over a suicided wife or something... by having an alien intelligence try to communicate through our own memories. The core idea of the story is classic sci-fi territory, if the presentation is a bit wonkish that's a stylish issue, but how is it much different in 'topic' than, say, The Uller Uprising from H. Beam Piper? Or perhaps more accessably: The Fuzzy Papers?
Dune again drips into that strange catagory of Space Opera that I mentioned earlier. There really isn't any science at all. Shiga-wire is a common feature in the technology, but what is Shiga-wire? Its a metal fiber taken from an alien plant root... if I recall the same plant that produces the Semuta drug (from the ashy reside of burning said plant), which gives you a better trip when paired with music.
Herbert, compared to Lucas, at least pretends to care about the process of science, but that's mostly because he is writing in the future and not in some nebulous 'galaxy far away', so we have names for the principles and processes, like the Holtzman effect.
But like Solaris, the actual purpose of ALL of this is to address universal human themes. I've mentioned it is an explicit response to the Great Man theory of History, and a reflection of Herberts own interest in Ecological Conservation. The technology might be handwavium (well, the idea of dynamic optics using liquids suspended in force fields is pretty hard science-ish, if you can replace generic and impossible force fields with a more practical idea, a flexible transparent membrane perhaps?), but the ideas and even the cultures presented are grounded very much in the real.
Is Space Opera sci-fi? You asked me earlier. I say it is, just very soft, and because I think Genre Assignment is a fools errand so I prefer to err on the side of easy communication rather than grognardy pedantry.