Please excuse some of my spelling in the titles as i didnt have enough room.
The best difficulties would have to be heroic as it still has a bit of a challenge to it. When i'm with my little brother (
i'll do normal or easy if i feel like slaughtering someone. But Metropolis is great, 2 player in legendary, especially when you get to the bit when the gauss warthog is because you both get snipers and have to use ur wit and snipe the jackal snipers before they snipe you. If anyone hasn't tries this, do it it is fun and gives you satisfaction when you finally do it.
p.s there is about 20 snipers, a few grunts that go on turrents (they take two shots in the body, 3 elites (1 blue and 2 red) then when you have killed about half the covenant, two blue or red elites in ghost come through a door.
Also even though this is only kind of relevant with the topic, what is your favourite campaign level in halo 2. Mine would probably be either delta halo, cairo station or outskirts there all good.