How to you play Crash bash in 4 players?

Yeaa 2 on 2.

To play four player campaign you need to either system link two 360s or you can do the coop online (each xbox has to have the game). You cant play four player campaign with just one xbox and one game.

Yes

You can use two wired controllers on a PlayStation 2. Then you will need Multi-Tap and two more controllers (wireless).

you have to have a multi-tap