Apple would have hit their pinnacle of tech innovation with the Newton if Jobs didn't come back.
Seriously, all their tech while he was gone was utter, regurgitated crap, lol. Sculley drove Apple into the ground, and while there's a lot of gripes to be made about Jobs on a personal level, he DID get them back on the path. he was an arsehole, but he also was a perfectionist. 10 different variants of overpriced, underpowered Quadra's wouldn't have done it for Apple under Sculley.
Anyone saying Apple would have done the iPod without Jobs' crew at the wheel is insane, and that project alone got them to their dominant, albeit elitist uber hipster position they now hold.
Without Jobs they would have just made another cookie cutter MP3 player versus inventing the ipod, which virtually destroyed the competition of the day, as did the iphone and ipad when they came out.
Jobs and Ive saved Apple from a very rapid. very public and very painful death. Sculley would have destroyed what was left of Apple in a matter of months, and their market value shows it in spades from back then. I remember when the ipod came out, I had a $600 20 GB Nomad Jukebox I just loved. I tried an ipod when they came out and never used the Nomad again, literally - the ipod was just so, so much better.
That being said, Jobs was no inventive genius. He wasn't an engineer, but he did know how to absolutely put the fear of God into his crew in regards to making very good products.