Is regional accreditation important for a masters degree?
The field of game design and development is relatively new and specialized.  The best potential employers are quite likely to know the reputations of institutions that offer suitable degrees.  Therefore, I would say that the reputation of the institution is probably more important than either the exact degree title or the accrediting agency.

You probably have a small number of target employers in mind.  Try to find out where their employees went to school.