The original point that the story is not told very well in-game is valid. However, there's a counter-point to be made that you get to play whoever you want to play, and if you want to play a guy who bashes what he's told to bash without going to the trouble to find out why, they make that possible. They also make it possible to read the game books and educate yourself (or your character). It's just like life, you can vote without ever having cracked a newspaper or watched a debate - in fact your vote counts the same as the other guy's.

Although it's not very clear in-game, according to the lore Alduin is there to end everything, not just the world but the Mundus itself. He ends the kalpa and things start over from scratch. How exactly this little tiny thing I bashed on the head and killed before the other heros could get over there to help me is planning to do that isn't clear. Which is a shame, really, because "Gee, that lizard wasn't any tougher to kill than the 75 other lizards" is probably not the takeaway Bethesda intended for their end boss.

I loved Sovngarde. I thought the music there was awesome. Kinda made me wish I was a Norseman back in the day so I could go to Valhalla!

That itself doesn't seem like much of a crime anyway. The world's religions are full of gods whose purpose is to destroy the world so that it can be remade, and in fact in many of them, the god who destroys the world is also the one who creates the world. From that perspective, Alduin's role (which, again, is not really made that explicit in the game) seems perfectly legitimate, and the only strong tie the player character has to him is as "that dragon who saved my life at Helgen". Given the available evidence, I would have let him live if doing so had been an option. Unlike Maven BlackBriar, whom not letting live was not an option... :/

Other than that whole, "cause the end of the world" thing, yeah, I guess he's a pretty cool guy.

What Allerleirauh said. Alduin's main goal is to end the world and start the next.

Considering that I have the collector's edition Alduin statue on my desk, I'm pretty disappointed with him ingame. Apparently he's a world eater but we see nothing of the sort. All we ever see is him acting the same way as a normal dragon. Also the player never even gets to speak with him. I guess I just feel he's not very fleshed out.

He does actually say that the Dragonborn would make an excellent slave at one point and much of his 'dragon speach' dialogue is particularly arrogant. ("All wither! I am your king.", "I will destroy your souls." )

In eating the present world and remaking another, Alduin would consume/destroy every soul upon Nirn. This is something even the mortality-hating elves aren't keen on. However, as the Towers of Reality are crumbling, one by one, perhaps Alduin's way is/was the only way mortality and physicality would be preserved. -ponders-