The leaderboards are currently messed up. Looks like everyone is seeing only 102 players listed.
Someone made note of this on the Activision Assist Facebook page and received this response:
"Thank you for letting us know, I will go ahead and forward it on to the correct departments. Thank you for all your support. ^MX"
Looks like other leaderboards might have been affected as well as seen on Activision Support Twitter feed:
Regarding MW3: "Leaderboards are currently undergoing maintenance on Xbox 360."