To me, and most likely just me, I find the inclusion of male nudity, and tasteful depictions of male/male sex to be where I define 'mature'.
While most games do not depict male nudity in any way I do hope that someday it will be included as much as the endless streams of female nudity. it will say. to me, that game developers have finally grown up and become more a mature about there own bodies and feelings. Naked men exist in the real world, however I find it odd that in video games...even in hetro sex scenes' they are able to please a woman with there pants on. Say what you will but to me a man with no shirt is not 'nude'.
Now to my second point...and to that I simply say 'dragon age' (I never played jade empire). To me those game represented a 'waking up' in terms of maturity. I know that most of the characters were Bisexual (even that's a step in the right direction), but for me it was such a nice fantasy world where men would flirt freely with other men and the only fear was a verbal soot down...not a literal one.
Also the sex between Zevran and the male PC was, to me, done with some amazing care that it was actually quite...good. it was like whoever directed the scene knew his stuff, knew what actually went on, and knew hot to not gloss over it all. It made for one hell of a sensual, mature and wonderful scene.
Just my 2 copper.