gondors armies vs. rohans

[Boromir88]

This is a good point. I guess my reasoning for this is the fact that Aragorn was the rightful King and ruler of Gondor, as where Gandalf wasn't.

Very true, and within the movies I think this works. Denethor is portrayed a lot worse and it seems like nobody cares that Gandalf smacks around the Steward, maybe they were just tired of the man...

An important point though that has been discussed before, as seen in Arvedui's claim and Aragorn's decisions, that it takes more than "right" to become King. One must have the support of the people, in which it seemed Aragorn did. The movies I think show this a little differently, that they were just tired of Denethor and wanted the true King. Where the books deal with it in a bit different way, Aragorn must prove himself to the people, (being victorious at the Morannon) to get the support of Gondor.