I really don't like WinShares as a metric because team success plays such a great part in calculating them.
I haven't found this to be as true with big men as with other positions, though.
As I noted, one of the top seasons after the Bird / McHale / Parish / Garnett / Maxwell group is Raef Lafrentz, and another is Al Jefferson.
If you want to go by PER, the top 30 is dominated by Bird / McHale / Parish / Garnett, with the next best season belonging to Big Al.
If you go by points per game, now Antoine shows up, but his scoring efficiency ... uh ... left something to be desired. There's one Dino season in there, too, but I'm not sure how much defense he was really playing.