None of those on the level of Djokovic/Nadal.
Edberg wasn't even a rival by the way.
WTF how can even someone compare Chang to Djokovic or Nadal with a straight face?
I honestly don't think that the competition post 1993 that Sampras had was any better than what Federer had in 2003-2007. Agassi could've made things a lot harder for Sampras, but apart from 1995 he didn't really start to play conistently to his potential until 1999 when Sampras was already sitting at 12 Slams.
Some of the years the competition was so weak - especially 1996-1998 and Sampras could only win 4 Slams in these 3 seasons aged 25-27. It's really his fault that he lost so often to people he should be beating thus creating this illusion that the competition was a lot tougher than it actually was.
That's the main difference between Federer and Sampras - both could play at an insanely high level, Federer just did it on a consitent basis and you needed people like Nadal, Djokovic or a zoning Safin or Del Potro to take him out in a Slam when he was in his prime. Sampras could lose to some absolute mugs right in the middle of his peak.