The films of Andrei Tarkovsky: A visual fugue" by Vida T Johnson and Graham Petrie, page 100:
"Tarkovsky's distaste for Lem's style of "hard" science fiction was confirmed, just as he began work on the film, when he, Romadin, and Yusov saw Stanley Kubrick's 2001, which all three viewed as an unnatural, sterile demonstration of future man's technological achievements (O Tarkovskom 165; A. T., "Zachem proshloye ... " 101).
As a result, they decided to make their film an exact opposite: the perfunctory attention paid to the journey through space, the run-down space station, the messy rooms, and elegant library -- overflowing with an extremely odd assortment of earthly objects -- were designed to counter the futuristic technology of Kubrick's film (Romadin Interview)."
We know nothing of what motivates Dave, Frank, Floyd or any other of the characters in 2001; in sharp contrast, it is the motivations of Tarkovsky's central characters that gives his film its power and challenges all of us to question our own innermost impulses.The same source (underview.com), in another section:
It could be said that "2001: A Space Odyssey" exemplifies the Western preoccupation with external, racial influences, while "Solaris" represents the most fundamental internal quest for individual [internal?] humanity"
From the perspective of Solaris, emerges a new view of the nature of man: a creature who soars off into the cosmos in quest of other worlds and greedy for scientific knowledge, without having explored his own labyrinth of dark passages and secret chambers, without discovering what lies behind doorways that he himself has sealed.
Although Tarkovsky gives us nothing as dramatic as a monolith or a cosmic light show, I can well imagine that Kubrick and Clarke may have felt some envy at his treatment of the alien theme, compared to which the 2001 version of alienness is rather remote and mechanical.
The film, however, is more convincing than 2001 and, ultimately, more satisfying as a taste of the truly alien universe that is likely to exist "out there" (if any such thing as an alien life form is ever found to exist at all).
In 2001, we witness the assisted evolution of mankind and its destiny with machines and higher life-forms. In Solaris, we see man as a distinctly un-assisted earth-bound creature confronted by forces outside his understanding, yet inescapably coming to the realisation that those forces are nothing other than his own fears and deeply-hidden yearnings.
``reviewers who deliquesced into mental jelly when 2001 hit the screens miraculously recovered to greet Solaris with comments like "The most intelligent and questioning science-fiction movie ever made" (Quote from Science Fiction Movies by Philip Strick, Octopus Books Limited, London, 1976.)
``Even given my own admiration for 2001, I have no quarrel with that statement. In fact, I would add that it is also the most beautiful..science-fiction movie ever made.''