RoboCop is definitely set in 1990-1991, by the way.
1. A TV spot places it in 1991.
2. RoboCop: Prime Directives places Alex Murphy's "death" in 1990.
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Since we know that the movie progresses into the following year, this is actually a pretty solid timeline. As a result, the second film is 1992, the third film is sometime in the 1990s, the Prime Directives show is set in 2001, ten years after the creation of RoboCop, and the upcoming game is set between RoboCop 2 and RoboCop 3.
The announced Dick Jones TV series would be a prequel set before the original film (assuming it's still happening), and RoboCop Returns is set at least after the original film, although it could be a different timeline beyond that (assuming it's still happening).
As for comics, most of them seem to be alternate timelines. The Marvel Comics series is set between RoboCop 2 and RoboCop 3, but it has some anachronisms in it and one of the covers places Murphy's death in 2015. Ignoring that, I guess it's fine. The Dark Horse series is a direct continuation of RoboCop 3, so it works fine in the original timeline.
1991 -
RoboCop
1992 -
RoboCop 2
1992 -
RoboCop Vol. 1 #1-23
1993 -
RoboCop: Rogue City
1994 -
RoboCop 3
1995 -
RoboCop versus The Terminator #1-4
1995 -
Dark Horse Comics #1-3, "RoboCop: Part 1-3"
1995 -
RoboCop: Prime Suspect #1-4
1995 -
Dark Horse Comics #6-9, "RoboCop: Invasions: Part 1-4"
1995 -
RoboCop: Mortal Coils #1-4
1995 -
RoboCop: Roulette #1-4
2001 -
RoboCop: Prime Directives 1x01-1x04