How many 'Great Tales' were there?

[gondowe]

This is the passage I refered to from the Letter Nº131, He was talking about the Tale of Beren and Lúthien:

There are other stories almost equally full in treatment, and equally
independent and yet linked to the general history. There is the Children of
Húrin, the tragic tale of Túrin Turambar and his sister Níniel – of which
Túrin is the hero: a figure that might be said (by people who like that sort of
thing, though it is not very useful) to be derived from elements in Sigurd the
Volsung, Oedipus, and the Finnish Kullervo. There is the Fall of Gondolin:
the chief Elvish stronghold. And the tale, or tales, of Earendil the
Wanderer. He is important as the person who brings the Silmarillion
to its end, and as providing in his offspring the main links to and persons in
the tales of later Ages.

Greetings