Ah well, with 3rd Planet - i was lucky to know of this for many years, but 'Guest' and many other things have come from talking to my russian lj friends:))

Also - when I was very small, I obtained a child's guide to Science Fiction films, the text was very juvenile but there were pictures of two films that had a very great impact Robinson Crusoe on Mars (ha ha! yes, of much less interest today!) and Solaris. The images, landscapes of Mars and interiors of spacestation really haunted me, as well as (something I realise is a signature now) the intense expressions and unusual figure groupings of Solaris, the seriousness of it. and so as soon as I could I saw both Solaris and Stalker.

As for what you say of Ender's Game, perhaps I have been spoiled by my enjoyment of Joe Haldeman's Forever War which is superb (imho) on similar themes.
http://en.wikipedia.org/wiki/The_Forever_War

As for films, well yes - most are crap unfortunately, but there are a few I have liked of (roughly) modern times such as:
A Scanner Darkly - http://www.imdb.com/title/tt0405296/

Dark City - http://www.imdb.com/title/tt0118929/

12 Monkeys - http://www.imdb.com/title/tt0114746/

Existenz - http://www.imdb.com/title/tt0120907/

Code 46 - http://www.imdb.com/title/tt0345061/

Chronos - http://www.imdb.com/title/tt0104029/

Pi - http://www.imdb.com/title/tt0138704/

Children of Dune - http://www.imdb.com/title/tt0287839/

Serenity - http://www.imdb.com/title/tt0379786/

The hitchhiker's guide to the galaxy - http://www.imdb.com/title/tt0371724/

the first Matrix movie aswell

and other films that will come to me as soon as i log off! ha ha! :)