Raikou could have been a Raichu the names are alike Suicune could have been an Altaria ( Suicune's mane looks like the clouds of an Altaria ) I agree that Entei was an Arcanine. But Suicune could have also been the female evolution of Snorunt ( male evolution of Snorunt is called Glalie if I'm not mistaken ) Then again Raikou could have been an Amphpharos or however you spell it.