Nirn is High fantasy, end of discussion. oblivion met the definition of high fantasy, both definitions. Since Nirn, Mundus, the whole realms are totally fictional make all TES games High by definition. this cant really be argued. Go to the Lore Forum to see the results.
Actually Nirn is not really High fantasy or low fantasy. It's stuck somewhere in between. It's creation is high fantasy but it's setting and how things function in the world are low fantasy. And yes, it can be argued, especially since Todd also considers TES to be low fantasy setting.
However, Lord of the Rings is pretty high fantasy.
Apparently you dont know about LOTR, Middle Earth is an ancient Earth.
No it's not, it's a continent, not a planet. Originally it was thought up by Tolkien as a fictional period in Earth but it was made very clear over the years by Tolkien and his son after him that it is no longer that fictional period he first envisioned and is actually far more with the Silmarillion. Wiki's tend to be outdated or wrong...