NBA:
My frat brother Karl Malone is probably the best player without a ring. Before his stint with the Lakers he rarely missed games b/c of injuries. He's 2nd on the all-time scoring list.
Charles Barkley is a close 2nd though. Patrick Ewing, Gary Payton, Reggie Miller, John Stockton. Jordan, Pippen, and Co. ruined alot of championships for all these players.
NFL:
Barry Sanders, Dan Marino, and Jim Kelly
Those three guys deserve a ring. Barry Sanders never had the supporting cast. Marino never had the running game needed to win a super bowl. And Jim Kelly had 4 chances and just couldn't get the job done.