CornPlanter
Emperor
Yes, I'm pretty bored and gotta kill some time 
These lists probably won't prove anything but we might see some interesting trends.
I'm going to exclude one leader from my list, that is Darius, because I always tend to do far better with him than my normal difficulty level. Otherwise my list would be like this: Darius, Darius, Darius, Darius, Darius...
1. Warlord - I started civ4 at this level. Dont remember the leader I first won with
But most likely Tokugawa back in Vanilla times. Used to play him a lot.
2. Noble - dont remember either.
3. Prince - Alexander of Greece. I dont remember was it Warlords of BtS already. Domination.
4. Monarch Toku of Japan, it was also my first enforced UN victory abusing vassals
BtS
5. Emperor - Pericles of Greece. Culture.
6. Immortal - Elizabeth of England. Domination.
7. Deity - it's unlikely I will ever give a shot at Deity. Civ 5 is comming...

These lists probably won't prove anything but we might see some interesting trends.
I'm going to exclude one leader from my list, that is Darius, because I always tend to do far better with him than my normal difficulty level. Otherwise my list would be like this: Darius, Darius, Darius, Darius, Darius...
1. Warlord - I started civ4 at this level. Dont remember the leader I first won with

2. Noble - dont remember either.
3. Prince - Alexander of Greece. I dont remember was it Warlords of BtS already. Domination.
4. Monarch Toku of Japan, it was also my first enforced UN victory abusing vassals

5. Emperor - Pericles of Greece. Culture.
6. Immortal - Elizabeth of England. Domination.
7. Deity - it's unlikely I will ever give a shot at Deity. Civ 5 is comming...