My kid went through a Friends phase not long ago, and so I got to revisit a few episodes, and... they didn't really hold up for me.
Favorite characters:
Chandler
Phoebe
Monica (sometimes)
Joey (sometimes)
For me, Rachel and Ross are funny if the situation they are in is funny, but otherwise I find them annoying. I REALLY do not like Ross (or David Schwimmer, for that matter). I get that the "whiny-ness" is part of the character and part of the funny, but it's still annoying to me.
Since it's come up, I don't find Jennifer Aniston all that attractive (Phoebe, on the other hand...) so there wasn't that enamored-ness about her.
One guest appearance that I thought funny was Fisher Stevens as the therapist that Phoebe was dating. "You and your stupid big cups, which, I'm sorry, might as well have nipples on them..."