The whole time I was listening to this, I was waiting to hear Mr. Mosquito, SkyGunner and R.A.D. Robot Alchemic Drive. If there were some PS2 games to ever be PS2 as heck, those three really take the cake. Not really essential (I kinda think they are), but definitely some When-I-Think-Of-PS2-I-Think-Of-These games. Really wish any of them would end up on something else, especially R.A.D. It could work with almost anything that has a number of buttons equivalent to a PS2.
Shinobi, too. That game would have me absolutely furious, but I loved it, the color scheme even made me think of the system hardware itself. It felt like a perfect harmony between Sega and Sony.