I agree with Nathan; the Third Hokage. Why? Well, besides the Tsuchikage (butchered spelling again I think) that is currently active, I'd say he is the only one seen so far in the series that has REALLY lived out his reign.
I mean, think about it; the guy was appointed when he was still young, and didn't die till he used the Reaper Death Seal to put away the first, second, and Oro's arms (too bad that didn't last forever). Even then, he retired from active duty to let Minato take over, only ot have to resume the position when he used the Reaper Seal to help seal the kyuubi. The guy was old, but like the Tsuchikage, he lived out the title of Hokage like it should. They don't make you Kage for life so you can just die in your prime. (sorry Minato and his counterpart in the Sand).
And, quite frankly, his fight with the First and Second (despite it seeming nerfed now that we look at Madara... But Madara probably wasn't fully tricked out with that Susano'o, or at least didn't have the rinnegan) is still one of those fights where, if you look at it, Hirzuen Sarutobi showed what it meant to be that Hokage with power, and actually being forced to use it.