Acting President Lee Adama can command me anytime:D.
I have a sneaking admiration for President Dwayne Elizondo Mountain Dew Herbert Camacho of Idiocracy.
But my real favorites are Henry Fonda in Fail Safe, and Frederick March in Seven Days in May.
Another vote for Jed Bartlet, who in addition to cursing G-d and putting a cigarette out on the floor of the national cathedral, told a religious fundamentalist, “Get your fat ass out of my white house.” 
Fictional presidents rarely face apocalyptic economic crises. But they always seem to be faced with incoming asteroids, Russian terrorists, etc…
How about James Garner and Jack Lemmon in My Fellow Americans? Talk about reaching across the aisle!
Heck, during the parade scene, it was practically reach around the aisle.
Jed Bartlett in a landslide.
Hail to the chief, he’s the chiefest of the chiefs?
I have a fondness, similar to a fondness for junk food, for President Whitmore in Independence Day. I can see the bad acting, the stiffness, the poor dialogue, but dammit, it’s Bill Pullman.