Sad but true:
Halo 4 peak number of people online in War Games:
100-120k
(This roughly a month after the game released)
Source:
HaloCharts Link
Halo 3 peak number of people online in Matchmaking:
200k
(This was noted January of 2009, 1 year and 4 months after the game’s release)
Source:
Google Sites link