Instructions
Examine the reflective side of the disc. The easiest way to identify genuine PlayStation 2 discs is by the color of their reflective layer. Genuine discs will be blue or purple if they are CDs, and silver if they are DVDs. Officially, black discs are PlayStation 1 CDs (sometimes it can be hard to tell the difference between a black and a dark blue or purple).
Examine the quality of the packaging and disc label. If the printing looks cheap (pixelated or washed-out), or is on sub-standard material, then you may be the owner of a counterfeit disc--even if the counterfeiting operation was high-tech enough to produce blue or purple reflective layers. Missing logos (such as for Sony, Dolby, or the game studio) are another giveaway.
Trace the origins of the disc. Large retailers, such as GameStop or Amazon, have controlled supply chains that make the appearance of counterfeit discs unlikely. If you got the disc from a smaller online store or from an online auction site, though, the chances that it may be a counterfeit are higher. Consider how much you paid as well. If you got a bargain that seemed too good to be true, then it might have been!
Try to play the disc. Fake discs will give a red loading screen warning the player to use only official Sony PlayStation discs. So if you unwrap your new game only to get such a warning when you try to play it, the best thing to do is return it.