The ones I think of offhand:
- Release type: physical release, or digital only
- Release regions: what regions saw an official release
- Region compatibility: is the title region-locked or region-free?
I understand that there's often complexity when it comes to what constitutes a "region" when it comes to release and licensing and all that. I wonder if there's a system that can be developed that would help as a rough guide - perhaps identify the most common cases, and use those, with a special category for ones that don't fit well into the others? I guess the main value is in identifying NA, Japan, and European-specific releases easily.