There are 23,768 people on the 360 BlazBlue leaderboards.
However, I just realized this doesn't represent every BlazBlue owner on the 360 not everyone has played a ranked match. I for one have not and am not ranked. Shadowblind hasn't either. It also doesn't account for the folks that aren't gold members.
Still, we got a reliable aproximate number to pin on the 360 blazblue. PSN leaderboards anyone?