Whenever my lawfully wedded husband starts grumbling about what he considers to be unrealistic details in James Bond-films (the last time, I believe it was the Russians piloting the wrong plane model...) I nod and go "Oui chéri, you're right, that is THE most preposterously unbelievable thing about 'Moonraker'"...
As for 'The Martian', my severe lack in space engineering skills should probably prevent me from being too categorical, but not much about this story of an astronaut forgotten on Mars - not to mention the retrieval of said astronaut! - felt in any way real to me.
Not that realism is always necessary in a film (or there would be no James Bond films) (I wouldn't miss them) but believability is! Coleridge's "willing suspension of disbelief" only goes so far, I'm afraid, where I'm concerned.
The actors here are top-notch, and the scenery spectacular. Still I wish Ridley Scott would stick to TV.