I think it depends on what 'era' you're into. Like 80s or 90s. Some people have different tastes and interpretations of what creative is. There's no doubt that Off The Wall, Thriller and Bad were more pop, synth-orientated. Due to the short space a vinyl record had at that time there was a constant focus on creating hit after hit, which Michael did marvellously. During the 90's (which of course has a different sound to the 80s) we saw the rise of the CD, allowing Michael more time and tracks to express himself. Moving away from Quincy, gave him a little more artistic flexibility and freedom too. The 90's from my perspective was more experimental than the 80s in terms of sound and flow. It was no longer just about pure pop hit records to Michael, but something deeper as well. More complex concepts, melodies and songs.
Creatively I think Michael has always had it. I mean come on. Look at Bad. He wrote all but two of the songs on that record - all the songs were international hits and FIVE of them went to number one in the US. Truly astounding.
The genius of Michael was never isolated to just one period of time. It's always been there. The 90s were an incredible period for Michael artistically, no doubt. But you cannot deny the creativity and magic of OTW, Thriller, Bad and Invincible.