Thanks for asking Sciere, at the first glance I think "Misty world of Cuchullain" fits both games as the Irish mythological hero (Cú Chulainn) is the protagonist (player) of both . But one can have a better look at this interview with the maestros of those games:
It looks like there no 'Irish Mythology' group? I'd thought there would be more games than these two based on other similar characters/stories; or would they just be grouped with Norse/Germanic mythology?
I would agree with that, but there's always the possibility of already existing or in the future beyond Gargoyle's other games related either specifically to Cú Chulainn or generically to Irish Mythology. I propose first that these two games belong to a specific group like "Gargoyle's Cú Chulainn series". Because indeed the Gargoyle's version of Cú Chulainn is present on both games, either in life or after-life.
Later adding both to more generic groups as Irish Mythology, etc., if already existing or in the future other/s in the database.