Everyone absolutely thought the original click wheel iPod, the iPhone and the iPad were all doomed to fail. Hell, the Apple watch didn't exactly get off to a hot start for that matter.
And back at the beginning, the Mac OS GUI. Yes, Steve Jobs saw the idea of a graphical GUI at Xerox Park, but what his engineers turned out is something completely different. And at the time it was easily as revolutionary as the touchscreen interface of the iPhone.
Actual duds by Apple that I can think of off the top of my head:
- The Cube
- The Mac IIcx
- The Mac IIfx
- Whatever that ungodly massive Unix box was that they branded as Apple
- The liquid cooled G5 cheesgrater