I pretty much only play Halo 3 Social Slayer, though my suggestion is applicable to all gameplay.
In recent weeks, I have been almost exclusively matching on the game’s worst maps. I can’t recall a single instance in the last week that I played on Guardian, The Pit, or Narrows (my 3, and surely everyone’s, favorite maps).
This begs the question, how difficult would it be to allow the players to select what maps they would like to play, and then match with other players? Or, at the least, revert back to the voting/veto days. But getting matched on Valhalla, Assembly, High Ground, etc. is getting quite old and frustrating.