Would love to have a HBO-like series that was based on the Horus Heresy from the Warhammer 40k tabletop game. I recently got into reading the books for a bit of fun commute digestible pulp-fiction a few months ago. With some structure such a series can run for a solid eight or so years.
My interpretation for the series would be a very dark, moody sci-fi version of Game of Thrones, basically. That is to say a series that plays it's fantasy straight faced, graphic and darkly.
I would also like to see live action films that based on DC comics which are not total garbage. Rather more Justice League Unlimited than whatever Suicide Squad, upcoming Justice League and Batman v. Superman is/was.
A series of horror films based on Tales from the Crypt would be neat too. Not many high budget anthology Horror films come about.
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I feel like more modern sci-fi is camp. I can not think of any aside from the Alien franchise that attempt to be 'grimdark' at all. Good guys always win these films, that is absolutely not 'grimdark'.
There is also the injection of humor, side kicks or levity too. Also, not what I think of as 'grimdark'.