Others are Danny Manning, Larry "Grandma Ma" Johnson, Richard Dumas (Suns), Ron "Hollywood" Harper before the injuries, not the guy who rode Jordan co-tail to a few titles, Brad Daugherty before the Nascar took his heart away, Chris Jackson before the Mahmoud Abdul-Rauf & health problems.
But #1 hands down if you can't count Len Bias, RALPH SAMPSON! Dude was the most un-stoppable force in all of basketball! 7'4 yet ran like a gaurd, grace of a SF, unparalleled athleticism paired with a picture perfect jumpshot coming from a dominant center. Very good FT shooter, shotblocker supreme & a Kareem Abdul-Jabbar killer at Kareem's heights. If this guys knees holds up through the duration of his career, maybe we were witnessing the best center of all-time & definitely would be worth the argument because he easily woulda won 3-4 titles in Houston with Hakeem the dream!
From what I've read, however, is that Hakeem and Sampson wanted to get paid, so I'm not sure if both would have stayed on the team long term. Sampson is an ideal choice. He was going to be one of the best ever but his frame was kinda fragile.
For anyone who has read Bill Simmons' book of basketball, he has a list of players whose careers could have been worthy of the hall of fame but twists of fate interfered. He named Michael Ray Richardson, Andrew Toney, James Silas, Marvin Barnes, Gus Johnson, Ralph Sampson, Brad Daugherty, Maurice Stokes, John Lucas, Sam Bowie, Terry Cummings, Roy Tarpley, Reggie Lewis, Grant Hill, Alonzo Mourning, Drazen Petrovic, and the Hardaways.
Kemp and Thompson are on his list of the 96 greatest players ever.