Remember the old HBO Guides? All the movies in there carried the MPAA rating and then handy-dandy abbreviations telling you why. I'd spend a good 20 minutes going through it looking for everything flagged with SSC and N -- because that meant Strong Sexual Content and Nudity. Holy shit, they even had R -- for "rape", which led to a very uncomfortable explanation from my babysitter when I (six years old) asked what in the hell that meant.
I realise that "GamesRadar" and "mature" in the same sentence is like matter and antimatter (or pasta and antipasti). But they've (rightly) judged that "adult" and "mature," as applied to video games and films anyway, usually mean T&A and lots of SSC and really immature depictions of both. So they've provided a list of games that actually do contain mature, as in grown-up, themes. You might be surprised to find Braid on here, but they sorta justify it. Warning, those expecting a chucklefest absolutely will not find it in the last two on the list.
Mature Games That Are Actually Mature [GamesRadar]