Yes he is the greatest.
Its a pity that he his cut throat exploits are focussed on by the press. But as some have said here already, people forget the past and only choose the remember the positives. Senna was unmistakingly brilliant, but he was a racer and if that mean't pushing the boundaries of what is acceptable driver behaviour then Senna would push that boundary. Suzuka 1990 is a perfect example.
It doesn't' help him either that the F1 press coverage we see is typically British-based, being a German sure does have to work against the guy in that regard. And arrogant? Just because someone puts on a "face" when dealing with the sly, scheming press doesn't make someone arrogant. Determined and focussed would be a better description.
One of the best ways to recognise Schuey's skills would be to recall his first win for Ferrari in 1996. Spain, pouring rain, V10 running 1 cylinder down and he still obliterated the field in a clearly inferior car. Whenever the conditions were mixed or wet, he always shone.
Its a pity Ayrton passed away, would have been awesome to see the two of them face off in the twilight years of Ayrton's career.
Looking forward to seeing Kimi get a decent, reliable car under him and see if realise his full potential. Bring on 2007!