The iMac was the right product at the right time.
- Inexpensive price, powerful processor - but it had no PCI slots, so it didn't cannibalize G3 sales.
- Joe Sixpack home users rarely use PCI slots - the iMac already had Ethernet onboard, USB took care of almost everything else.
- The colors got people to notice Macs. It was a huge refresh, these machines look different, they are different. Think Different and buy one.
A lot of the work on the iMac was already started with Steve Jobs came aboard, so it can not be entirely attributed to him.
The Cube is a different story:
- Too expensive. Tried to be as powerful as a tower G4 in a tiny package, but most people would rather have the bigger cheaper G4.
The Mac mini got it right - small size, small price. That's an ENTIRE computer in there - and still pretty powerful (but not as much as a G5 or Mac Pro).