For me, it is Seinfeld. I love that show. All 9 seasons were great. Kramer and George were perfect. George has a direct link to my funny bone, and Elaine was such a fox. Even Puddy was a good minor character. Oh how I miss Seinfeld.
Seinfeld. Friends is prolly the most overrated show out of those three imo. It does have funny moments, but it those a bajillion times in subsequent episodes. HIMYM is better that Friends, but not as good as Seinfeld.
Easily Seinfeld. For some reason I see an episode of HIMYM on TV that I've already watched and if I don't really like it I can't watch it again, but that's never the case with Seinfeld. The rewatch value is really great. Maybe because of the randomness and nothingness of the show which is what made it great.