I'm not really sure exactly what Steve Jobs brought to the table at Apple.
Love him or loathe him, his impact not only on Apple's success but popular culture is undeniable. Anyone who says otherwise is just being argumentative and is probably jealous.
What did he bring to Apple? Well, aside from being a literal genius, he brought a vision. He didn't want to run a company that just made electronic products. He wanted a company that changed the world with its electronic products. He wanted to produce things that changed people's lives. He wanted to produce things that were both aesthetically pleasing and easy to use. One of Apple's underlying design philosophies has always been to create products that the work for the consumer, not against them.
The perfect example of this is the iPod. The iPod was a late-comer to the portable digital music market. There were already several companies producing several lines of MP3 players. What Apple did different (yes, that's incorrectly spelled on purpose), was to make the devices consumer friendly. That's all. Hell, on paper the devices weren't even that spectacular, often having much lower storage capacity and fewer features. But they made the product work FOR the consumer and not against them.
That simple design philosophy was what sparked the revolution. Suddenly everyone and their dog could figure out how to use an iPod and subsequently wanted one. And they did exactly the same thing with the iPhone. Entire businesses switched from Blackberries to iPhones over night, something which businesses are loathe to do, simply because iPhones were far easier to use and their employees actually used them instead of fumbling around pretending to.
Of course, as an Apple fan, I've always felt that the MacOS was easier to use than Windows, it just took the iPod, iPhone and iPad for everyone else to realise it as well
Now did Steve do all of this by himself? Hell no. But after being kicked out of Apple, he was forced to become less of an arrogant bastard and more of an accomplished businessman. And the first lesson he learned in order to succeed, was to surround himself with brilliant people. And thus was born Next and Pixar.
When he finally came back to Apple, it was in a shambles because the whole company had lost sight of that original vision. It had turned into just another computer company, producing just another computer, and given that it was competing against a more popular brand, it offered very little reason to buy it.
Steve had also become not only a master businessman, but also a master salesman in his time away. And so he fired half of Apple (literally, there was a period where Apple employees feared getting into an elevator with Jobs because they knew there was a good chance they'd end up unemployed by the time they got out) and employed most of his Next buddies and some of his Pixar buddies. And of course he'd made a lot of friends in other areas too like the CEO of Oracle and Google and brought them on board as well.
He changed the culture of Apple into one of dedication, passion and obsession. His employment philosophy was that if you didn't love what you were doing and didn't want to dedicate your every waking moment to doing it, then why should he employ you?
Like or hate Apple products, like or hate Steve Jobs, I think it's hard for anyone to legitimately claim that he isn't a brilliant man.