Pokemon's First Appearance: Pokemon Gold, Silver & Crystal

With the second generation of Pokemon games came two new -eons: Espeon and Umbreon. (The latter didn't make it on the list, unfortunately.) The former is better than the previous three because it can learn attacks that each one is weak against. Espeon also has a 525 base stat total, as well as good speed, power and stamina. However, it is weak against Bug, Ghost and Dark attacks, and doesn't have a great selection of non-damaging and damaging moves. But it can kick the asses of Jolteon, Vaporeon and Flareon, which is what matters most.