1984 was pretty good:
Michael Jordan
Hakeem Olajuwon
Charles Barkley
John Stockton
Those guys are all arguably top-five at their positions, all-time.
Other players were guys like Alvin Robertson, Sam Perkins, Otis Thorpe, Kevin Willis, and Jerome Kersey. 2003 was deeper, but I don't think any draft has had four elite players of the quality that '84 did.
Yeah, to this day everyone crucifies Portland for drafting Bowie because they missed out on Jordan. But selecting Bowie looks even worse knowing that Portland ALSO missed on Hakeem, Barkley and Stockton. Ouch. Portland made the Finals twice in the early 90s with Clyde and co. - imagine if they had one of the '84 class HOFers in that mix...oh what could have been...
Hakeem went #1, Bowie was #2. And Bowie probably would've been an All-Star caliber player if he didn't have the bones of an 80 year old woman. Still no Jordan, of course. And Oden shows they didn't learn their lesson...
Classic draft mistake to help us all forget about '01: in 1985 Dallas picked Detlef Schrempf (and traded him before he got good), Bill Wennington, and the immortal Uwe Blab in the top 17 picks. Players they passed on include Karl Malone, Joe Dumars (3 times), Terry Porter, Michael Adams, and Arvydas Sabonis (all 3 times).
I think '03 is gonna be up there - right now it's a Top 5 class and maybe #1 in total depth. Depends how the main guys' careers wind up working out.