Do you Consider Pokemon Like Darkrai to be Legendaries?

I really don't get why Gamefreak made the Mythical Pokemon title, when the only difference is that they can only be caught in events. That is the only difference between the two. Other than that they have the same lore and legends as Legendaries, they are super rare like Legendaries, and extremely powerful, like Legendaries. In my book they are Legendaries... Yes that includes Phione unfortunately.

Yes. Declassifying certain Legendaries as "Mythical" is nonsense. It's unnecessary and doesn't make much sense either, considering certain Legendary Pokemon could be classified as Mythical in terms of their importance to the games or the world at large. It's rubbish. Legendaries are Legendaries.