I was moreso talking about the GA. Because of JLU she's more associated with the League than Black Canary or any of the other female Leaguers, minus Wonder Woman. She's easily the most requested female member to join, up there with the likes of Martian Manhunter and Green Lantern in requests.
If I had to rank, I'd say:
1) Wonder Woman
2) Hawkgirl
3) Zatanna
4) Black Canary/Vixen
6) Mera/Jessica Cruz
Done with DC. Can't handle the constant whiplash! Time to go on a hiatus!
Like Green Arrow, Black Canary started out as a second banana character but she managed to keep coming back and become one of the most important JLA members and then with Green Arrow become an important solo character. Granted she was in an ensemble series (while Ollie himself was dead), but she was the lead character in BOP. She's had a much stronger publication profile than Zatanna and Hawkwoman--who get to appear in a series for a bit and then disappear for long stretches of time. For most of DC history she's been the number 2 heroine, next to Wonder Woman. And unlike the powerful Diana or Kara or Zatanna, Dinah is in the same class as Green Arrow, Batman and Mr. Terrific as a street fighter. So she makes a nice contrast to Wonder Woman.
All the more reason to hope the movie doesn't bomb. If the movie fails that spectacularly DC might give up on the title. Even if they don't cancel it, they might decide to not waste good talent on it. A far worse fate I'd argue than having Harley forced on the team. At least a good enough writer can make Harley on BoP interesting. A bad writer on the title? Doesn't matter who is on the team then.