Never. The Big Bang Theory doesn't have longevity, and I doubt it ever will. I can't watch the older episodes anymore and find them that funny. But I still find almost every episode of Friends enjoyable.
Never watched Friends. I watch BBT sometimes, it's only funny when there is a scene with Amy, for me. It's good to watch but I do think it is overrated.
Not at all. Friends is such a great show because all the characters are irreplaceable. You can't get rid of one of them without screwing up the friendship dynamic that made the show so great.
In The Big Bang Theory, all you need is Sheldon and people that aren't as smart as him. That's what makes the show entertaining. A few of the characters could be killed off and the show wouldn't be affect. Sheldon and Penny bring the most to the show.