"What does an otaku like to do?"
An otaku is defined in Japanese as someone who has an obsessive interest in something. I think in English, this is more associated (and possibly misinterpreted as) with someone who is obsessed with manga and anime. In English, this carries a generally negative connotation.
In Chinese, I believe this is more associated with those who like to stay home for their leisure time and don't like to go out. The 宅stems from お宅 (Japanese for otaku), and used to be more similar to what the original definition of otaku was. However, sometime within the last couple of decades, 宅(男/女) was taken more literally as someone who stays home.
So, in summary, I don't think otaku is an exact translation of 宅男, but there also isn't really a better translation, and it also reflects the slight negative connotation of the Chinese phrase