Auri-El is the elven equivalent of Akatosh, and is actually one of the chief deities of the Altmer's pantheon. The Altmer believe themselves (and also fellow mer) to be descendants of Auri-El, so it isn't a far stretch that an elf could be the dragonborn. And plus, it's Akatosh's blood. He can do whatever he damn well pleases with it.
While the male (or even female) nord is the most obvious interpretation of the Dragonborn, it is far too generic and boring for my own personal taste. Its what the people of skyrim would expect. Imagine how Nords would react if they found out that the dragonborn was an elf, especially a female elf. There would be denial and rage. But one day, they could see the dragonborn not for the color or texture of their skin, not by the pointiness of their ears, but for their actions. And from this, they would be better able to see past race in the future (hopefully).