I like to believe that in pretty much epoch (as far back as the Cambrian period) that sustained complex life, there was always the potential to become intelligent, and that more often than not, such life would exploit that potential.
Just imagine; there could've been civilizations that predated humanity, possibly even tetrapods or even chordates, by eons and we don't even know it.
I really don't know... Crows seem to be better tool builders, but some parrots can be smart enough to talk and socialize with human beings. I'd still put my money on Parrots, but I'm not sure if anyone knows the answer.