Quote: "the multi player is best for maybe 1 on 1 and probably 2 on 2"
I have built multiplayer levels with 8 players and some have done 16.
I have built two multiplayer games.One with 4 players and one (with two additional betas) with 8 players.
Good level design and proper use of switching back between single and mp mode to build your game.
My main concern in a mp game is high speed fragging so there's a limited amount of frills in my mp games so the speed is quicker.
There are other mp games (s4real made a great one) that require stealth and the list goes on.
Failing at every guitar game ever made!