You mean musically or by his appearence?
Because musically he was the best on Invincible and Dangerous. Followed closely by Bad.
Physically, he was the strongest on Bad. Just looking at the Bad tour makes my head explode.
However, I really like his appearence in 2008 and 2009. He didn't look young and reckless but also not tired and fragile. It just seems like he was getting back into the groove and being all modern.
It is so genius the way he evolved his costumes. From the Thriller red jacket to Bad renegade and gangster look, to Dangerous futuristic and History military outfits...nah, it's just too much to even put in a single sentence.
And don't get me started on each small detail like the glove, finger bands, armbands...
This is so incredible about Michael, you can study him on so many different levels that it never gets boring.