This is pretty hard, because I tend to think of Dredd more in terms of phases rather than individual stories, but also because most of the stories I HAVE read since about 2000 have been the big individual (graphic-novelised) sagas. BUT I haven’t read eg Day of Chaos yet, so I’m not up to date.
But I’ll have a go. BTW I’m going to exclude the stuff written by my brother from consideration here, so my judgement is unsullied by family ties ;)
THE JUDGE CHILD QUEST: As a kid we had the Titan Books editions of the main Dredd sagas - Cursed Earth, Apocalypse War, Judge Child - we didn’t have The Day The Law Died but a friend did. I had to pick one, it was almost the Apocalypse War, which is a proper story (unlike the disconnected travelogue of Judge Child) but for wonder and pleasure Judge Child wins. As a demonstration of the scope of the Dredd Universe, it’s unbeatable, and it starts and ends very well - the grotesquerie of Faro The Garbage God at one end, the inexorable Western-style executions of the doomed Angels at the other. In between, so much to enjoy: “That damned moustache!”; “Shake hands with the Thing From The Pit”; McMahon’s drawing of the exploded planet-thing; “Two aliens have entered the battlefield!”, and even one of Wagner/Grant’s verse stories that’s actually bearable. Add on the epilogue with Dredd on the streets while his fate is decided by the Council of Five, just to tie a bow on it.
UNCLE UMP’S UMPTY CANDY: One of the classic early years one-parters, the one with the absurdly addictive sweets. To be honest, this is a stand in for about fifty stories published in the early 80s, especially in that relatively happy (for Mega City One) time between Cal and the Apocalypse War. What I like about these short stories isn’t just their craft - satire, action and a good gag or two in six pages, week-in week-out - but the overall sense of Dredd in what he might consider his prime, before the losses started mounting up and the doubts set in. Portrait of the Judge as a Young Man - one who enjoys his job, banters with his colleagues, rolls his eyes at the citizens… it’s as close to a stable, sympathetic environment as a comic with a fascist protagonist ever really gets. The Complete Case Files 3-6-ish are probably where you want to look for these, I don’t know exactly which stories are in what.
THE DEAD MAN: The actual story of the Dead Man is slow but fine, this is only really in here for having THE great Dredd Universe revise-everything-you-know-RIGHT-NOW-EARTHLET cliffhanger. I bought it when it came out. I probably squeaked. And, er, I’ve sort of spoiled it just by its inclusion in a Dredd Mt Rushmore.
BEYOND THE CALL OF DUTY: I simply haven’t read enough of what you might call Late Dredd to make a call on the best one, so instead here’s a highlight of what you might call Middle Dredd, or Dredd: The Procedural Years - it was this or The Pit, which is fantastic (Dredd takes over an underperforming Sector House - hijinks ensure), but this one has the gloriously creepy and awful Judge Roffman in it, one of those foils who, once he’s appeared, you can’t believe a series ever managed without.