A lot of game developers are really concerned about games not being taken "seriously". It's always been my opinion that if you have to ask for someone to take you seriously, you are not worthy of serious attention. If people find your content to be meritous, merit will be given. My concern about the lack of mature themes in games is personal. I think most games have uninteresting stories that explore irrelevant or trite subjects and they are really boring as a result. I don't care about pitting technology against nature; it's a trite theme. If it hadn't been explored in dozens of games already, it might be interesting. I don't care about focusing on high-level concepts like the "nature" of good and evil; it's far removed from anything I deal with on a daily basis and it is usually discussed in an explicit, heavily didactic manner.