Why are Buddhas always Indian, male and human?

Dipankara, Siddhartha Gotama, Maithreya to name a few (*of the 28 named in the Buddhavamsa*) - it feels a bit like a Hollywood plot where it's always only an all American hero that fights off the alien invasion of planet Earth. Given that the dharma is universal why isn't a Buddha a deva or a Pacific islander or a woman? Why is it also always only one person and not like say a united nations of Buddhas?