No it's not. Am I cheating if I buy a bigger TV and can see enemies more clearly at range or notice them quicker? What about if I buy an elite controller and have extra buttons on the back so I don't have to take my thumbs off the analogue sticks, giving me a distinct advantage over non-elite players?

This isn't cheating. This is the same as buying an elite controller, this is people willing to invest more money to have an advantage. Cheating would modifying the game's rules to gain an advantage, like an aimbot. No game had any rule, as far as I'm aware, that states what controller one must use.

Also, you suggest banning these people? Potentially costing someone 100s or 1000s of dollars, over a game?! Could you be any more butt hurt or spiteful? They're just games. If this is your reaction to losing, then you need to take a long hard look in the mirror.