I'm more of a That 70's Show kind of guy, but it helps I watched it only a few years after the main characters were. So it was perfect for me. Friends never clicked and Seinfeld... It's fun, but that's kind of it.
Father Ted, Black Books and Count Arthur Strong are quite popular in my family. I've never been able to watch much of Seinfeld or Friends, they just don't resonate with me, but I know they're both well written and somewhat innovative.
I can watch any ep of Seinfeld but very few of Friends, usually there's some giant Ross relationship drama happening that is insufferable to sit through. If they had a lot more Joey and Chandler stuff, and way less Ross, I'd like it more.
I'm a huge Seinfeld fan, watched every episode multiple times. Watching Friends for the very first time now. Seinfeld is definitely far more funny and consistent, there were only a few real dud episodes and characters.
Friends has entire huge chunks of the show that are just utterly mediocre, usually involving Rachel and Ross. Some of the episodes early in the show involving the two of them really make it hard to continue watching. It does get a lot better by season 6 or 7 where it gets a bit more light hearted and breezy. Still, we're at the point where if its a Ross heavy show we are skipping most of it. I can't really say that about any Seinfeld character.
Plus I really, really like how in Seinfeld there is the underlying mandate of "these characters are awful, and they will learn NOTHING." That makes for awesome comedy. Friends tries to be way more sitcom-y with characters growing, learning, etc. Great for real life, not great for a sitcom.