Nice guy syndrome basically describes a guy who will listen to his female friend's every complaint, rant, problem, and experience in life; will help them out no matter to the cost to them; would die for their friends without even thinking; but can never get a girlfriend.
“好人综合症”说的是这样一类男人,他们会倾听女性朋友无止尽的抱怨和唠叨,听她们倾诉自己遇到的问题和人生经历;在她们遇到困难时会不顾一切帮她们走出困境;甚至会不假思索地为她们放弃生命,可她们永远都不会成为他的女朋友。

All their female friends will continue to go out with mindless, stupid men who treat them badly, and hurt them over and over again, never even considering the nice guy, because he is “such a good friend”.
他的这些女性朋友会继续跟一些毫无头脑的愚蠢男人约会,被他们粗鲁对待,并且一次次被伤害。而这些女性朋友从来都不会考虑跟这个好人约会,因为他是个“这么好的朋友”。