Who do you think are the "core" franchises in the big 4 leagues?

who do you guys think are the "core" 4 to 6 franchises in each league? by core, I mean most historical / most well known / most influential / most successful or however you want to define it. My own list:

nfl: steelers, 49ers, packers, cowboys

nba: lakers, celtics, knicks, bulls

nhl: original 6

mlb: yankees, red sox, giants, dodgers, st louis