MLB: Cal Ripken Jr., 2,632 games, May 30, 1982-September 19, 1998
NBA: A.C. Green, 1,192 games, November 19, 1986-April 17, 2001
NHL: Doug Jarvis, 964 games, October 8, 1975-October 10, 1987
NFL: Jim Marshall, 282 games/Brett Favre, 279 games, September 27, 1992-Present Day
Edit: Technically, Jeff Feagles holds the NFL record for consecutive games played, but he's a punter so...