In all of everything what system has the best graphics? Including things like Wii (even clearly not) and older systems. I think it is really between Xbox 360 and PS3.
Personally, I don't have an X-Box 360 or a PS3, and the PC game with the best graphics that I've played on so far was Half-Life 2... But, based on trailers, gameplay footage, and playing demos in malls etc., I've come to the conclusion that PS3 has greater graphics capabilities than the X-Box 360... Note that I said capabilities; not all PS3 games neccessarily have extremely good graphics. If it was based on the demonstration of best graphics concerning only the best of these 2 systems' games, then I would be a bit stuck between Metal Gear Solid 4: Guns of the Patriots for PS3 and Halo 3 for the X-Box 360. Both have simply insane graphics, but I'm slightly more inclined to believe that PS3's better As for PC games, well, most of them can be played on other platforms, so for that it really depends on the version that you have. But all the same, Metroid Prime: Corruption (for the Wii) has really good graphics too; compared to the 360 or PS3 it's mostly a matter of subtle details and slightly more advanced performance.