If he's a competitive online gamer, then such a large monitor is overkill. He'll be moving too fast to appreciate the decreased jaggies that comes with using a higher screen resolution. As far as I'm aware, the higher resolution is the only advantage of a larger screen with first-person shooters. It's not like you can "see" more of the game world with a larger screen than you can with a smaller one. And as others have mentioned, it's hard to get good framerates at such high resolution with today's hardware. When I've seen serious competitive gamers play, they dial down the resolution and graphics effects to ensure steady framerates. And if you decrease the resolution, it'll look even blockier on a larger monitor.
