The menu populations are not accurate and are an unknown because they do not explain what they include. Does it include campaign, menu surfing, private matches, ect.? As far as multiplayer goes Ghosts has more people playing multiplayer than Black Ops 2. I've tested this many times:
Test
Ghosts: 118k
BO2: 78k
Ghosts +40k lead, 152% BO2 population