Zany
Prince
Please propose what leaders you think are missing. Not civs, leaders.
Remember, you don't have to suggest what you think are better choices than those included in Civ IV, just those you think are also good choices. Please specify if you do think your choice for a leader is better than what the developers chose. 
America - Abraham Lincoln, come on, he was in Civ III. But I do think Washington is a better choice and Roosevelt is okay, but this is an example
of Civ IV trying to be something else, something new, but then it becomes something bad.
Arabia - Abu Bakr! Obvious, but I do think Saladin was a better choice when you only get one leader for this civ.
Aztecs - No clue.
China - Again, no clue, but there must be dozens of good choices.
Egypt - Ramses! Nobody wants Cleopatra in. After all, that does not represent true Ancient Egypt. And was she really a great leader? No, she just famous.
England - How about a King?! Not sure what is the best choice though.
France - They made great choices, because Joan of Ark was not an actual leader of France!
Germany - Also pretty good choices, and they are placed well chronologically. Frederick in the days of Prussia and Bismarck representing true Germany.
Greece - How hard could this be? How about Pericles, he's just the first one who pops into my head.
Inca - No clue, yet again.
India - Good choices, Asoka represents an older India which I wanted since my first game of civilization (which was Civ III) and met Gandhi. Also, did Gandhi actually ever hold any form of Indian public office?
Japan - Another one that should be easy to come up with another leader for, but for some reason I am having trouble think of one with.
Mali - Is there any other known leader besides Mansa Musa?
Mongolia - Perfect choices, no one could replace Genghis and Kublai.
Persia - Xerxes or Darius. Why does this civ, above all others, have only ONE leader?!
Rome - Come on! How about Trajan?
Russia - Pretty good choices, but Stalin would represent another period in Russia's history.
Spain - I know almost nothing about Spanish history. You suggest a proper male leader.


America - Abraham Lincoln, come on, he was in Civ III. But I do think Washington is a better choice and Roosevelt is okay, but this is an example
of Civ IV trying to be something else, something new, but then it becomes something bad.
Arabia - Abu Bakr! Obvious, but I do think Saladin was a better choice when you only get one leader for this civ.
Aztecs - No clue.

China - Again, no clue, but there must be dozens of good choices.
Egypt - Ramses! Nobody wants Cleopatra in. After all, that does not represent true Ancient Egypt. And was she really a great leader? No, she just famous.

England - How about a King?! Not sure what is the best choice though.
France - They made great choices, because Joan of Ark was not an actual leader of France!
Germany - Also pretty good choices, and they are placed well chronologically. Frederick in the days of Prussia and Bismarck representing true Germany.
Greece - How hard could this be? How about Pericles, he's just the first one who pops into my head.
Inca - No clue, yet again.

India - Good choices, Asoka represents an older India which I wanted since my first game of civilization (which was Civ III) and met Gandhi. Also, did Gandhi actually ever hold any form of Indian public office?
Japan - Another one that should be easy to come up with another leader for, but for some reason I am having trouble think of one with.
Mali - Is there any other known leader besides Mansa Musa?
Mongolia - Perfect choices, no one could replace Genghis and Kublai.
Persia - Xerxes or Darius. Why does this civ, above all others, have only ONE leader?!
Rome - Come on! How about Trajan?
Russia - Pretty good choices, but Stalin would represent another period in Russia's history.
Spain - I know almost nothing about Spanish history. You suggest a proper male leader.