Personally, I'm a giant history geek. For that reason, choices like Wu really, really get under my skin.
I want my Civ leaders to have done something extremely worthy, at least more than just something like a trivial "first leader to do blah" "first blah leader."
Wu was the first female leader of China. good for her. She deserves a cookie, but not placement above Taizong, Qin Shi Huang, Mao, etc.
For that reason, I'd also be angry if they replaced Rameses with Cleopatra, or brought in Elenore Roosevelt as leader of America (she was in Civ2, wasn't she? As America's female leader.)
For the most part, Civ4 didn't fall into this.
Hatshepsut... eh, she didn't accomplish much, but she was atleast fairly notable for more than just being female.
Washington... I'd still prefer to be replaced with a more deserving figure. Jefferson, FDR, JFK, Lincoln, maybe even Einsenhower. He'd be neat, accomplished a lot but normally glossed over in terms of his presidency.
Boudica... was alright. I'd have preferred Vercingetorix over Brennus, though. I mean come on, when you think Celts, you think Vercingetorix.
I also want the same of my civs.
I want civs that have done at least a few notable things. That's why I'm against adding the Zulu instead of another sub-Saharan African civ (Congo civ would be neat.)
It also bugs me that Firaxis does, kinda, put too much of an emphasis on Europe. I want to see more Far East and Middle Eastern civs. Instead of just "Arabia", we could have Arabia (Caliphs/Saudi only), Libya, and maybe either Israel or Pakistan.)
Also, and this is what bugs me about Elizabeth and Victoria both being English leaders... why not make sure each leader represents a different aspect of the civ?
Like for England you could have the explorative/colony-loving Elizabeth, the modern Churchill, and the old Crusader Richard I.
For Arabia, you could have Harun al-Rashid to represent the heavily scientific and cultural era of Arabia, Saladin to represent the bloody middleage wars, and then Ibn Saud to represent modern Arabia.