Okay everyone I was just trying to think of the most powerful benders of each respective nation and I got a few ideas, feel free to give input, I welcome it greatly!
Air - Aang ( Kind of by default though I guess!)
Water - Master Pakku (Katara is good, very good, by Pakku has got about 4 to 5 decades on her)
Earth - King Bumi ( I guess Toph is a possibility, but Bumi is over 100 years old...come on!)
Fire - General Iroh ( I could see a case being made for Fire Lord Ozai, maybe Princess Azula, but that is about it)
Guess I should mention I am only thinking of those who are alive at the present time, just in case any of you were wondering. Thanks!