I first saw the Who back in 1976 when Keith Moon was still alive. They played the old Boston Garden, and came out, performed two songs, and Moon collapsed over the drum kit, and they couldn't continue.
They announced that they'd return at the end of the tour, and when they did (on April fool's day, no less), they walked on stage with Daltrey announcing "we haven't forgotten..we owe you one". They then played the most powerful show I've ever seen (and I've seen literally over four hundred concerts in my life); two and a half hours without pausing for breath.
At the end of the show, they smashed all their equipment, and fans stayed for a half hour screaming for another encore, but there was nothing left to play on!
The headline in the Boston Globe the next day; "The Who pay up..all debts settled". I think that summed it up nicely.
I've seen them 18 times since. They've had some great shows, but that one was purely biblical in nature.
I saw Led Zep a couple of times as well. They were really good, but no one is The Who. The best live band there ever was, and still pretty damn powerful in their early 60's!