Pokemon theory question?

ok...just this my imagination yake me beyond my capacity of brain hope that my qustion is not to difficult,think the regions of pokemon had taken from japan only but if u take areas from india and other country the world of pokemon including legendaries will grove vast and there will be more than 500 generation of pokemon think...please tell me reasonable answer..because these qustion had taken me beyond this world i had taken at least 5 years of think it...please..