That may be because they keep trying to water it down and dumbify it into generic sci-fi action crap. The original movie was acidic, satiric, and gleefully sick, and Peter Weller's performance held it together. Murphy's struggle to reclaim his humanity amid everything being done to him that could possibly dehumanize him - being gruesomely picked off, resurrected as a would-be corporate tool, losing his wife and son in the wake of his death, to finally having to take out Boddicker and his cronies for good - gave everything else in the film more weight, IMO.
Unfortunately, every spinoff they've done lacks any of that and just milks out the same old cliche elements that they were poking fun at back in 1987 - corrupt businessmen, big brutish killer robots, psychotic drug runners, Dirty Harry justice - without ANY of the spirit or imagination of that first film.