The co-op experience seems to be out of favour in recent years, which is why I love good old games like this. We happened up Judge Dredd only because GOG brought it up before us, and my son has taken to some of the charatcers instantly (Dredd and Death in particular). I've even had to buy some of the Big Finish audio dramas!
The game shares more in common with the Big Finish audios than with the original comic creation IMHO - both having smaller casts caused, presumably, by budgetary concerns (and of course it is a good OLD game - PCs were less capable back then). Having said which, not being flooded with ordinary citizens that you should ignore does not hurt the game at all as far as I can see. My only REAL complaint is the brevity of the game - it is only 11 levels long. vaguely similar games like the Dooms, Heretics and Quakes of this world are typically 3-4 times this size I beleive.
I really wish there were add-on packs, third-party levels, or even a sequel - it's been fun to play this, and we'll be returning to the world of Heretic far too soon simply because we run out of Dredd fun :(