You seem to have a poor grasp of causality. The endings are the endings. Motivation is supplied by the player. The very nature of player choice in a game means that there's no other source. All the game can do is create a world with sufficient verisimilitude to make it feel like your choices have meaning at the time you make them.
Yes, the issues are with the verisimilitude of the world of New Vegas. There are not an infinite number of choices, of course. Games, such as these, by definition have structure and rules that limit the number of potential moves. Thus, my issues are and have always been global with the rules at large, the framework that serves as the backbone for the potential narratives. You insist on looking at things from within the dollhouse. I am looking at the framework of the fa?ade, the artifice of the edifice, so to speak.
Also, you're coming off half-cocked because of some obsession with Fallout 3 and you're assuming a lot about my opinion about Fallout 3. That's apples to oranges. My complaints are New Vegas specific. New Vegas is an orange that wants to be a delicious blood orange. Is it? That's the debate. Time and the world outside these forums have already proven Fallout 3 is a good apple, but you don't need to like apples.
That you find the endings unsatisfying is a valid criticism,
I've already made this point. The only exception being the House ending. But that's only part of the problem.
but complaining that they don't offer post-facto motivation (a contradiction in terms if I ever heard one) for your actions is ridiculous.
Huh, is this a point you wish I made? Because I never did.
Now if the endings are wildly inconsistent with your actions, that's a bad thing, because it ruins the suspension of disbelief. But if your gripe is "I fought for the NCR and only got this stupid medal, wtf", that's nonsensical. What were you expecting?
The endings are wildly inconsistent with your actions, yes. A civilian medal for an incredible military victory is the epitome of wild inconsistency. Also, the motivations for your actions leading to the ending are not believable.
You're also abusing the term "canon" as applied to games. There's no way all of the endings can be considered "canon" as they contradict each other. There's only one canonical ending, and at this point we don't know which that is because the devs haven't told us. Your use of the word "canon" is both confusing and incorrect.
This is confusing. You're just reaffirming my stance about canon with this point. Are you saying I'm not saying this? Because this is exactly my point about canon. This tells me you're not reading what I write, but you're taking the time to respond. That's...strange.
There's going to be one canonical narrative, the structure of which has to work within the universe created in New Vegas. This is the problem I have. A perfect Fallout New Vegas game would mean any of the four paths could believably be canonical (for clarity that's one at a time). In reality only one is believable and another is barely believable.