Steve Jobs is one of the Apple Co-founders, and as such I think he probably owns a good number of Apple's shares.
However based in his Net worth: $5.5 billion (2010) (via Wikipedia) and the total equity $31.64 billion (2009) of Apple (via Wikipedia). I think he could at best own a little part from the company.
As far as I understand he is no more the Apple's owner. he should have at least the half of the company shares plus one, to have a totally authoritarian vote in the boards of directors. right?