Good argument, except that in Halo 2 on the hardest difficulty level, if either of you dies the game reloads from the last checkpoint. It's immensely hard at first, but soon you learn to love what it does to the difficulty. Of course the hardest difficulty adds a whole bunch of enemies and makes them harder.
Really, Halo games should be played in multiplayer, don't even pretend to show any kind of degrading argument(this isn't pointed to you Allan) if you haven't blasted your way through with a good friend and then went over the best points again later on, when the adreline rush has left you. Halo gave me the same kind of insane glee that Goldeneye had, that freakin' Dynabomber had the first time. It's the feeling of finding something new and enjoing it immensely.