In what sense did the iMac G4 fail to live up to the hype? That was my first Mac, I still have it. Thought it was an incredible computer for the time--the iMac + OS X 10.1 Puma was absolutely magical coming from Windows 98 on a beige Dell.

The design still looks incredible too, 20+ years later.

I will grant that the Newton failed. In the Apple hardware category, I'd also add the iPod Hi-Fi, the butterfly keyboard, and the touch bar.

That said, Apple's failures are rare and their multi-decade track record of delivering on hype is unsurpassed.