He's still a great player, but he's not THAT player anymore.
You don't see Cassano leaving for Argentina, except because he left for Italy when he was in a foreign country in which he totally flopped and behaved like a little bitch. He's also not the kind of player to happily sit on the bench...
2009- 2010 Villa was arguably one of the best strikers in the world, for both club (Valencia) and country. He was only overlooked because of monster seasons by Rooney, Drogba, Ronaldo and Messi, and for not playing in a more famous club.
If only both our forwards were better than Tevez :D
Anyway, there's 17 strikers in that list and Tevez is better than at least 7 of them, funny thing you mention Cassano and Higuain though.
I'm guessing that he'll keep training with City even if he's not playing to keep himself fit.
He'd go to Juve for about 7-8m wages i'm guessing (if the hunger is still there), but he would be a really nice transfer for you.