This is a pretty subjective statement. It seems that a lot of Duarte's designs are somewhat derivative. Material extends MS's Flat design. I'm also not sure how much of that is Duarte, its a pretty open secret that Google makes use of some pretty high end digital agencies who aren't allowed to let folks know what they're working on.
WebOS was pretty tacky though an interesting OS design - actually implemented better by LG on their SmartTVs.
The Sidekick may have been his most interesting product but it was completely broadsided by the release of the iPhone and was n't anywhere near competitive to the Blackberry so I'm not sure how innovative it was.
If anything Duarte's had pretty good record for working on products with innovative features but never necessarily ground breaking on UI/UX