
Now in shooters, certainly not unique to Halo, there is more often than not a marked difference between playing through the campaign and playing with and against other people. Campaigns, be they solo or two player, tend to be you and whatever meager allies accompany you against a veritable horde of enemies (albeit not always all at once). Games involving human teams and opponents just require a slightly different skill set. Campaigns need players to be able to fulfill one objective after another while shooting at mobs that are shooting back at you, and while they can be numerous, these mobs and their abilities tend to be very scripted and relatively simple to out think and maneuver. Games against human opponents can be more or less the same, but the key difference is that you are up against opponents that are not scripted and, odds are, have out thought and out maneuvered the exact same enemies that you have.
While being great at one doesn't necessarily guarantee being great at the other, skill in one area does make it easier to adjust and adapt to the other. I suppose I'm banking on the hope that facing off against an opponent in a first person shooter is more or less the same as facing off against an opponent in a real time strategy game in that it all comes down to being able to read your opponent and reacting accordingly. I guess we'll see!