With Mario, it's a plumber saving a princess by killing everything in your way. Of course, we know why that won't work. I can just imagine adding angst elements.
I'd probably lie laughing playing a Mario game with a mature plot.
Heck I dunno, it could have mature humour or something, it doesn't need to be hefty serious or anything.
Of course, there is also audience that you have to be careful not to alienate.
What about Still Game? I haven't heard any opinion from you about that. I understand Series 1 is pretty crappy and Series 6 is bad too. But Series 2-5 is golden in scottish comedy.