"Men see women, women see men."
Translation:גברים רואים נשים, נשים רואות גברים.
Technically you should be right, because 'nashim' means women, 'anashim' means men.
However, it is very common to use 'anashim' with reference to both genders. You could say it also translates to the word 'people'.
In this specific sentence we talk about men and women separately, so it's important to emphasize the difference. Therefore it's גברים instead of אנשים