Apple Watch, AppleTV, and iPad, sure.Agreed. But other first-gen products include (not an extensive list) Intel iMac, Intel Macbook Pro, Intel Macbook, Intel MBA, Apple Watch, iPad, Intel Mac Mini, Apple TV, etc.
But something like the Macbook Air is totally ambiguous IMO. It wasn’t Apple’s first laptop or their first Intel laptop. It had a new name, but names are arbitrary. It had a new form factor, but so did the 2013 Mac Pro, and we don’t usually think of that as a first-gen product.