Interesting. I went probably 5-6 years ago and we were underwhelmed. He was kind of indifferent and didn't really act much like he wanted to be there. We were disappointed.
As for Celine, I went just because and didn't expect to like her, but was blown away. Probably the most perfect show I've ever experienced. She set a perfect time, flawless voice, genuine personality. Truly inpressed.
Probably my other best concert that was surprising. WIllie Nelson, again just went because he was a legend and left with great respect.