Dude, I'm the best halo player in the group of my friends that play halo. I have seen every skill level. The reason why most people suck at halo is because they do not know the maps, do not use the weapons strategically, do not aggressively fire with weapons, do not effectively melee, do not pay attention to their radar or (in halo 2) other allies' icons, and do not know the "economics" of the game.
For instance, if you know an enemy has the sword, put distance from you in relation to all possibilities of attack. Smashing the right trigger? I can nearly kill anybody not attacking with a sword, vehicle, or sniping weapon just by firing a few rounds and then throwing a grenade. Usually I just see people carelessly throwing grenades in easily dodgable patterns, especially novices.
Halo very much can evolve into a game of intellectual necessity. Very few venture to take the game that far and usually end up always outdone by someone that has.
Snipers must be dealt with immediately by whoring the sniper yourself or using vehicles. Nothing else would work unless you are on a map with enough hiding places.
Rocket whoring will eliminate any close to mid range threat and all vehicles. Problem is keeping it full of ammo.
You might say whoring is sooo retarded and unfair. However, isn't this a vague illusion to life? Don't some people whore, I don't know, lots of money? All that whoring is unfair makes it more difficult for others to get their hands on money, but they didn't get that money by just sitting there.
Seriously, those who absolutely dislike Halo should try to learn the game first and get good at it. It is a very enjoyable game. Don't judge a book by its cover and the first few paragraphs.