Ray'z Arcade Chronology Review (Eocene)
Great compilation of RayForce, RayStorm and RayCrisis, the latter two featuring alternate versions with higher res graphics.
Sadly, it's not the definitive Ray collection - it doesn't feature RayStorm HD, the coveted R-Gear prototype demo some Japanese editions have, or the extra content from Layer Section II, the Japanese Saturn version of RayStorm.
So you're not getting much you can't play in MAME, which makes the price a bit steep.
What you're getting though are excellent ports of superb and influential shmups - Kamui, Soukyugurentai and Crimzon Clover clearly derived a fair bit of inspiration from them.
I have a lot of love for this series so I can't help but recommend it.