Madden 360 will look far and away better because it's using a more advanced graphics engine. The PC version is bascially a Hi-Res PS2/Xbox version, that's all.
Compare the PS2 or Xbox version to the 360 or PS3 version. Most will take the latter. I will say this that the PC version looks sweet but it's running on an old engine.
Keep in mind that with next-gen consoles not only do you get a graphics overhaul but the gameplay gets better as well. The PC/PS2/Xbox versions do have their limitations regarding graphics and gameplay because all three are using the same game and graphics engine.