I agree that he started getting wobbly around the Diamonds and Pearls era. There were a couple of unlistenable songs and some filler on that record. The Love Symbol album was even more uneven. Newpowersoul and Chaos&Disorder were the lowest points of his recorded output...

...but that being said, he always has at least a couple of good songs on every album. And I've enjoyed the all of the albums since the Rainbow Children. Nothing's equaled his 80's input but they've been pretty solid albums. The first half of 3121 is probably the highlight of his recent recorded stuff for me.