Well that certainly plays a roll in it. The firenation also seems to be more of a military based nation... kinda like the spartans ^^;...cept...with mad kung fu skillz and fire commin out the wing wong >.<

yes there all like soldiers, military, fight, war, FIRE. And the earth kingdom and the water tribeseems like they just want to be left alone.

That could be why they're losing, then... The Fire Nation is more militaristic, more disciplined than the Water Tribes and the Earth Kingdom... This could play a role in why they're winning the war... (And if they do have more benders, that would help, too...)

If the earth kingdom was more like the fire nation then i think that they could win the war. They should become allies with the water tribes.

Since the fire nation is so military based, they could be training soldiers at an extremely fast rate, or looking for benders. I've also noticed that the fire bender soldiers aren't that good at firebending, maybe the fire nation is just teaching them how to shoot fire out of their fists and thats it, off to war. Maybe thats why they have a high soldier output rate.

Yes. they always seem to be getting their butt kicked. It really doesn't matter how many firebenders you have if they're all lousy at bending.

I agree. That seems likely. Most of the Firebending soliders that you see are not good at bending, and, has been said before, lose. There are notable exceptions among them though... (Zhao, Jeong Jeong, Zuko, Azula, Iroh, Fire Lord (I assume).)

Also, lets look at who they're fighting. Firstly, the air nomads were groups of people with no organized army, sure they probably had great benders, but we don't know that. We can only assume they had small malitias held in their few temples. The water nation consists of two seperate societies who due to distance could only make poor joint efforts in defending against a the massive fire nation...also look at the weapons of the southern water tribe, simple weapons made of bone and whatnot. If not for the fact that water benders abound and the hostile nature of the northern tribes territory, they would have fallen with the airbenders. In anycase. Also, the nature of water bending dissallows them to mount massive offensive movments like the fire nation, because they need a source of water to be effective.
The earth nation still stands because from what I remember most of their cities and villages and the like are on one big ol continent. Also they obviously have a large army and their bending style favors all but combat at sea. Feh, Im sure Im missing a couple of points, but I gots the sleepies, rawr.

It's almost like firebenders deal in abosolutes, their either good or horribly bad, hardly any intermediates. If the fire lord wants to win, he needs to step up the training for his soldiers, i swear a 5 year old could beat them.