As I peruse the list of eligible contenders, only 3 are truly prominent: Ironhide, Jazz, and Jetfire.
Ironhide would seem the most likely. A highly respected, experienced, war veteran, old world philosophy, and the kind of bot you would share a pint of oil with at maccadams. However, I think Ironhide would think too much with his spark, and not with his logic circuits. A leader has to have a strategy, think critically, and make sacrifices in the name of the greater good, and unfortunately, I believe, he would rather sacrifice himself first.
Then there's Jetfire, the scientist. Much like his counterpart Shockwave he is able to put aside all "feelings" and make critical decisions, ones that will surely lead to victory, but lose morale points, as he sends his plasma-cannon fodder comrades into the field from his perch in Iacon. Sometimes the cold, hard, calculated approach doesn't always get the job done when it comes to a war of attrition, and you need your bots to rally behind you.
That leaves my choice, Jazz. I believe him to be the perfect mix. As Special Ops commander he has the ability to strategize, adapt, innovate, all the while keeping a cool head. He has the respect of his teammates and can throw a wicked party. Plus, wouldn't you love to see what he would look like after he receives his Matrix upgrade!
(some concept art would be greatly appreciated from all you talented folks out there)
Although I know Jazz Prime souds lame, he makes the best choice, and you all know it