I saw 40000 players in one playlist on Halo 3, and it was a playlist that isn't even available in Reach (Social Big Team, yes I know, I only played one game in it, don't go crazy) Then I went onto Reach later on and there was over a million players on it. How would that million be on Reach if the servers were displaying eachother's information?
There are still over 100000 people on Halo 3, clearly more than 4000 hahaha.