I’m not too sure what is characterized as the ‘best’, but in terms of critical success, sublime script writing and acting…it’s Frasier.
I know it isn’t the most quotable and not the most popular in regards to viewership, but it always won the most Emmy Awards (37 in total) during a sitcom golden era of shows including; Seinfeld, Friends, Roseanne, The Nanny, Everyone Loves Raymond, Will & Grace, 3rd Rock From The Sun, The King of Queens, Becker, The Drew Carey Show.