Great question.
Nitro beers like Guinness, Murphys etc use the faucet's restrictor to break out the co2 and nitro from the beer giving you a glass of basically flat beer with a thick creamy head. Doing this means finding a place to get mixed gas, applying it correctly and having the right faucet. I want to do this myself, I have the faucet, and have found a shop that will fill a co2 tank with the blend.
There are non stouts served this way, though: Boddingtons, Belhaven, and Old Speckled Hen are some example of non stouts in a nitro can.
Most people prefer most beers to be carbonated, though. Co2 adds some bitterness and crispness, I imagine Miller Lite would taste awful as a nitro beer.