He's a far better 'footballer' than the rest of our CMs and many in the league. He drives forward with the ball positively, can pass, can cross and can score. Sissoko is anything but limited. Erratic, inconsistent and possibly unorthadox but not limited.
There's so many midfielders in the league that define limited before Sissoko. The numerous safe passing/good in possession types that are in vogue for start.