That's akin to saying, "Who cares if we're playing football in 3 feet of sand? The other team has to play in it too, so there's no advantage."
It's not about having an advantage. It's about having a system that gives you the best controls. You know, controls? Arguably the most important thing to a great game?

Why do console fans continually bring this up like it's a legitimate advantage? Do you really need to see a photo of my desktop hooked up with an HDMI cable to my 42" Plasma? PCs have been able to do this as long as the Ps3 and 360 have been around.
It's all a matter of opinion, man. I like the way the control feels in my hand and I don't care about it being less accurate than a mouse and keyboard.
As for the graphics. I know it's significant. it's just not significant TO ME bec. graphics of the games I play already look beautiful and any better graphics wouldn't matter. surround sound, 50 inch tv's, and the fact that most of the people I know don't game on pc or laptops, makes XBOX a superior medium in my view.
Split screen sucks. And what's preventing you from taking a computer with you? I can take a laptop over to a friends and we can game together with no problems at all.
It's huge. You just haven't stopped to notice how vast the difference is.