Wow... you guys talk alot about the hokages. makes me wonder if you guys have forgotten about the people who cant become hokage because of obvious reasons, im talking about Itachi, at 18 he can most likely take on jiraiya and win. oro is afraid of him. Not to mention he has destroyed his entire clan.. if you ask me this is a real show of power.
The fact that the 3rd knew all of the Kohona jutsu's wont matter, since itachi can easly copy everyone of them since they arnt blood lines, also itachi more than likely knows numorous jutsus from other villages that sarutobi does not.. this also brings me back to the fact that itachi is only 18 and is obviously not in his
prime 
think of the damage he could do at the age of 30 or even 50 after he has had time to develope himself even further.
As far as the 4th goes, we know hardly anything about thim other than the fact that he became hokage at an early age.. had a couple of amazing jutsus and also defeated kyubi at the cost of dieing. The fact of that is that Itachi never had a chance to fight kyubi and try to defeat him, and Itachi HAS learned alot of amazing jutsus prolly more so than the 4th.