Your system is definitely faster.
But will PC games look better on your system than Xbox games? That's another question... Xbox games are meant to be played on nothing less than a Geforce 3 (a little better than a GF3 actually), while even the newest PC games still work fine on a GF1 or GF2. Of course you'll be able to run those games in higher resolutions, AA, Aniso, whatever, but that doesn't add polygons and better lighting. Xbox will have more aliasing and lower res textures, but since you're playing it on a TV, it doesn't matter.
So right now, Xbox games look better IMO.
btw, my PC is a P4 2.4, 512MB DDR, Radeon 9700 Pro, and I have an Xbox also.