The Rolling Stones. Obviously. It's just getting embarrassing to watch and they aren't contributing anything new to music anymore.
Totally agree with U2. You can only put out so many albums that are full of songs constructed around the natural reverb of a stadium. And most of them don't even make it into the stadium.
I think Pearl Jam still have some live tours in them, but there last few albums have been totally and utterly underwhelming. It's been a very long time since their music has had that 'spark'.
But I'm on the fence. If people are still listening and still coming to shows, and it's making the fans and the musicians happy, then so be it. Pearl Jam releasing a POS every few years is rally nothing for me to get worked-up about (but I wish people didn't care so much when the Rolling Stones go on tour.)
Additionally, I don't think twice about Herbie Hancock still playing live, or Ornette Coleman releasing new albums, or anyone like that, but maybe that's because those guys keep moving forward and haven't rested on their laurels.