I saw Janis twice. First time in 1968 at the Westbury Music Fair on LI with Big Brother and the second time at Woodstock with the Full Tilt Boogie Band. I really liked Big Brother and didn't care for the Full Tilt Boogie Band. It may have also been that Janis was whacked on heroin at Woodstock to the point where she almost didn't perform but I thought leaving Big Brother was a mistake for a number of reasons. James Gurley was one of the first psychedelic guitar players, somewhat crude but none-the-less very effective at creating the vibe that was needed for the music they played. Mickey Hart talks about seeing them on acid shortly after arriving in SF (he had never dosed before moving there) and how James Gurley "blew his mind". He had never heard anyone play like that.
Agree about all members of the Band being excellent musicians, writers and vocalists.
When the first Led Zeppelin LP came out it was a game changer in a lot of ways but I thought they were a pretty terrible live act and hate Stairway to Heaven. I was already a huge Who fan when the first Zep LP came out, IMO they were one of the best live bands I ever saw and way better than any LZ live material I have heard to date . I slept through Zeppelin's set at the 1969 Newport Jazz Festival, they closed out the festival, three days of tripping and I just couldn't stay awake any longer. I did see Jimmy play with the Yardbirds in early 68 and he sounded great but mainly played the parts and solos that Jeff or Eric had written. I saw him jam in a NYC recording studio in 1985 with Keith Richards, Ron Wood, Danny Kortchmar, Paul Shafer and Steve Jordan a week after Live Aid. I thought Jimmy sounded pretty lame in that context. They were playing old R&B covers and just messing around but I left four hours later with the sense that they all sounded much better playing music they had written, rehearsed and created parts for. Jimmy was quite a creative studio musician and the Zep LPs, tracks he recorded with Donovan etc. make that abundantly clear.
Interesting premise for a thread but I tend to think that you can have a great "band" without anyone in the band being a monster player. Conversely it is hard for one guy or woman to shine without a decent band which may be why I am having a hard time coming up with any examples of my own.