Actually, the fans are the ones who depict Alicorns as being naturally beyond the levels of regular ponies. The cartoons have never really stated that alicorns' powers are superior to those of all other ponies - certainly they have more than the regular pony, but if they are more powerful, then Starlight Glimmer is an Alicorn-leveled Unicorn as she is capable of fighting Twilight on equal footing. Indeed, the comics post another theory - that one must be a powerful magician to become an alicorn, so under that theory, its possible the only reason any of them became Alicorns to begin with is because they were as strong as they are now.



Alicorns don't actually 'rule' anything by nature - this is just what they do. Unicorns once did both Celestia and Luna's jobs, though I suspect they stopped having to once they took over. Exactly how many unicorns it took to raise and lower the sun and moon is unknown. The books claim it took several, though these aren't strictly canon, so your mileage may vary.



Alicorns aren't really 'aspects' - Twilight wasn't really anything, and since becoming Princess of Friendship she hasn't fundamentally changed anymore than any of her other friends. Her title as Princess of Friendship is essentially a glorified badge saying 'you exist' as she doesn't really do anything she couldn't already do. Her personality change is, far as I can tell, just poor writing on the writers' parts.



Insofar as magical theory goes, I have a theory that alicorns aren't a natural race - rather, they are a result of magic experimentation that is a closely guarded secret. Of course, the cartoon will probably prove me wrong on that, but I like the theory.