I don't spend a lot of my time in this section of the forum, but from the posts I've read, it seems that each deity isn't just the same deity for each race -- they're all different aspects or variants of some sort of universal pantheon, so they're the same but not the same, since each race views each deity differently (with some exceptions, I'm guessing).
I haven't seen anything about Akatosh being in the Nordic pantheon, only Alduin.. and that was pre-Skyrim. Now that we "know" Alduin is the son of Akatosh, has he replaced Alduin in the pantheon?