I'm a fan (and you should be too) because...
Firstly, he can sing well, his voice is extremely fit for rock song.
Secondly, the style of his song is mad and rock, with strong rythem, mad and crazy voice, crazy guitar of Randy Rhoads, Jake E. Lee, Joe Holmes, Zakk Wylde... That's a perfect band.
Thirdly, his songs have different style, like when we compare 'Bark At The Moon' or 'Crazy Train' and Goodbye To Romance' or 'Dreamer', it's totally different, but both of them are also amazing!
Forthly, the lyrics of his songs are crazy and mad.
Fifly, Ozzy is mad and crazy! His performance in concert is 100% crazy, he has good performance on stage! (Unfortunately,he has never been to Hong Kong, at least for a concert:()
That's why I am hypnotized by Ozzy Osbourne, one of the the greatest rock singers on the Earth!