Riley, 67, won five NBA titles as head coach, four with the Los Angeles Lakers featuring Magic Johnson and Kareem Abdul Jabbar, and one with the Heat, and was named NBA Coach of the Year with three different teams (Lakers, New York Knicks and Heat).
His 21 total postseason appearances, including a string of 19 in a row from 1982-2001 as a head coach, are two ahead of Boston Celtics' Hall of Famer Red Auerbach.
"I was the most blessed coach of all of them. I was," Riley said in receiving the award before the Heat played the Oklahoma City Thunder in Game Four of the NBA Finals.
"I had the greatest players with the Lakers, in New York great players in Patrick Ewing and John Starks and Charles Oakley. Came down here with Alonzo Mourning, Tim Hardaway, Caron Butler, Dwyane Wade, Shaquille O'Neal. I've been truly blessed."
Riley focused on building the Heat after leaving the coaching bench and assembled the current Miami powerhouse featuring a Big Three of LeBron James, Dwyane Wade and Chris Bosh, who decided to team up in their free agent year.
"That's a terrific honour," said Heat coach Erik Spoelstra, who was hired by Riley. "His impact on coaching, the winning and the championships that speaks for itself.
"But what he's done here with this franchise and this community, to build us into a year-in, year-out team that matters and a contending team, and he's done it in a different role. I think that's pretty amazing."
Miami players also praised the impact Riley has had on the team.
"He's like Big Brother that's always watching," Bosh said. "We know that he has that championship pedigree. He has a lot of knowledge in this game, his experience is vital to what we do."
James said just being around Riley was inspirational.
"He put together this team, and we just look at his résumé.
We look at his experience either as a player, as a coach or as an executive. He's done some great things.
"He's been around Hall of Fame players and guys who have won championships, so any insight that he gives you, he's giving it because of experience. He knows all about it.
"It's great to have him around and just hear those stories about some of the greatest players to ever play this game.