Question Call of Duty multiplayer game question?

[Dragonborn2712]

Hello,I want to buy some older version cod game for playing multiplayer.Im interested which is best to buy,which has a lot of active online players?Except newest modern warfare which is expensive.Long time ago I used to play modern warfare 3 over teknogods...Tnx in advance

 

[Dj0gany]

Black Ops 1