There are so few "anniversary" game releases that are actually on time. Some are remakes or sequels in a long running series, but all purport to be released on the anniversary of an important release date, that usually being the first game's release.
So let's name a few "anniversary editions" and assign them a number based on how close their releases actually got to the correct date. The closer to the exact year+month+day, the more points. 1 point for the right year, 2 points for the right year and month, and 3 points for the right year, month, and day... and 0 points for completely missing it.