3) Noah Daniels
I was hesitant to put Daniels on this list because he was President for about half a season. He only took over after Wayne Palmer was almost assassinated.
But Daniels deserves a special mention because the guy was a gigantic asshole. As vice-president, he tried to authorize the implementation of racial profiling and detention centers. He ordered a nuclear strike against an unnamed country despite the opposition of most of his cabinet. He had one of his advisors prejure herself to try and steal the presidency. Worst of all, he tried to have Jack Bauer arrested. Douche.
2) David Palmer
As President: Seasons 2 & 3
Also appeared in Seasons 1, 4 & 5
I never thought there would be a better President that David Palmer. His friendship with Jack was great and you always knew Jack was in good hands.
Palmer was a good man, but unlike the current crappy President, made tough decisions that weren't always the "right" thing to do. That is what is missing from Taylor.
Anyway, Palmer survived multiple assassination attempts till he was killed in the season premiere of Season 5. Still, he always seemed Presidential and was a great ally for Jack.
1) President Charles Logan
As President: Seasons 4 & 5
Also appeared in Season 6
There was no better President than Charles Logan (as portrayed by Gregory Itzin).
He took over after President Keeler was incapacitated after Air Force One was shot down. The character grew from there.
During his time as acting President, Logan was a sniveling, cowardly worm. He decided to lead from a bunker instead of the Oval Office because he was scared for his life. He was completely unprepared to make any decisions. You wanted to reach into the TV and smack him around.
He had David Palmer come in and make all of his decisions for him. Logan was also known for throwing a temper tantrum like an insulted school girl when he didn't like something.
Then in Season 5, Logan really hit his stride. He gave in to terrorist demands over and over again, sacrificing the lives of 11 Americans in a mall. He was even prepared to let his wife and the Russian Prime Minister be killed, but they were saved by Aaron Pierce.
Logan also invoked martial law, was complicit in the assassination of David Palmer and the selling of nerve gas to terrorists. He also ordered the murder of one of his Secret Service agents and threatened to have his wife, Martha, committed.
Logan also decided to take on Jack Bauer (always a big mistake) by having a warrant issued for his arrest, then ordering a navy jet to shoot down a passenger plane Jack had...um...commandeered that had evidence of Logan's illegal acts. With help from Martha, Jack eventually kidnapped Logan and tricked him into confessing all his illegal acts. He was arrested and currently lives under house arrest.
But all these acts were played so well by Itzin that you just HATED Logan. To give a comparison, his portrayal of Logan is on par with Michael Emerson's portrayal of Ben Linus on Lost. He is just a guy you love to hate.
Logan's most heinous act may have been having sex with Martha in-between a three minute commercial break. When the show went to commercial, they weren't even partly undressed. Charles Logan was also a minute man.