Why Vaporeon Is Overpowered
Vaporeon has a base Attack stat of 186.
Vaporeon can only learn Water Gun as its basic attack. Water Gun is 10 power and has an attack interval of 500ms. You can attack twice per second with Water Gun(1000ms/500ms). The effective power is now 20 but Vaporeon also gets a STAB boost since it is Water-type. This brings Water Gun up to 25 effective power (1.2520). Multiply his attack 18525 = 4555. This puts Vaporeon's DPS at 7th highest. Combining this with the fact Vaporeon has one of the biggest health pools and a decent defence makes him the top pokemon by far at the moment It's no coincidence you see Vaporeon at the top of many gyms.
So why does evolving my Evee into a Vaporeon make it so much stronger than Flareon or Jolteon? Jolteon, like most electric-types, relies on his speed. As discussed earlier, this hurts his base stats which is why you will see an Evee that turns Vaporeon having 25-30% more CP than an Evee with the same CP that turns Jolteon. That extra CP is an indication of the extra HP that Vaporeon is getting which is roughly double that of Jolteon's. On top of this, Jolteon's only basic attack Thunder Shock has a base DPS literally half that of. Theoretically if they were to fight a Vaporeon should walk away with over half his health remaining after trashing a Jolteon! Similarily, Flareon's Ember deals similar DPS to t-shock (11.9). Luckily for Flareon his evolution comes with extra Attack(238), which still isn't valued as highly as HP, but better than Speed. Although slightly higher attack than Arcanine, his other stats are lacking in comparison. Compared to Arcanine's much higher HP and DEF paired with his 15 DPS Bite which would do similar damage to an Ember vs Super-Effected targets, Flareon with a dps value of 2833 can barely even compete against top-tier pokemon with fire moves as lacking as they are. The only seemingly semi-viable Fire pick is Charizard. And that's only when you use him with Wing Attack, a flying-type move!
So how do we counter this monster of a mon Vaporeon? Well, right now you do.. The only pokemon that can even come close would be Venusaur. But thanks to 1.25x0.8x effectiveness, Venusaur boasting a respectable 3808 grass DPS value with a decent Defence, just barely loses to an equal Vaporeon because of Vaporer,. HP advantage. Exeggutor can also come close, but lacks the grass-type basic move to seal the deal.
Personally, I can't wait for trainer battles to come so we can have nothing but 6v6 Vaporeon battles!