In the context of asking someone how they feel, for example, and they respond with "never better," typically what they mean is that life has never been better to them than it is right at this very moment; also, it could mean that it simply does not get any better than it is right now.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi