And the gerbils are all shiny, if you're into that sort of thing. But anyway...
Raikou: Zap Cannon, Weather Ball, Aura Sphere, Extremespeed
Entei: Flare Blitz, Extremespeed, Howl, Crush Claw
Suicune: Sheer Cold, Aqua Ring, Air Slash, Extremespeed
Celebi: Leaf Storm, Recover, Healing Wish, Nasty Plot.
"I'm killing Skitty right now!"Let's look at this for each one:
Raikou: Zap Cannon is functionally useless in a world with Thunderbolt TMs (Voltorb Flip notwithstanding), and Extremespeed gives him a little bit of priority. Weather Ball is fun for Rain teams and even Hail teams (100 base Ice! Suck it Gliscor!), but oh mama, Aura Sphere. Ghost + Fighting is still resisted by little to nothing... and the ones that can take Shadow Ball + AS don't like getting Thunderbolts to the face.
Entei: I have to say, the fact that they're playing to this very blog with Crush Claw is amusing enough (hey guys, it's supposed to go to Dunsparce). Still, Howl makes Extremespeed and the long-awaited Flare Blitz extremely potent - so the question is, who's your physical Fire, Entei or Arcanine? Entei has Stone Edge and Iron Head, but Arcanine has Intimidate... hrm.
Suicune: Probably comes out of this with the least - let's face it, Sheer Cold is BANNED YOU *redacted* in most serious battles and it needs Extremespeed the least. Still, Aqua Ring could be a real pain in the rear on something with these HP/defense stats, and Air Slash is nice for coverage if nothing else. (So much for Ludicolo stalling it out).
Celebi: It only gets one new toy, but what a toy it is. The question is, does Celebi have the defenses to pull off more than one Plot before it gets hit with one of its multiple weaknesses and dies or BPs out of there? It's too bad Celebi doesn't have a tail, though - flavour-wise, Nasty Plot is one of the last moves you'd expect to see on Celebi.
This is part of the joy of post-release content for Pokemon, though - this may be the craziest post-release thing we've seen since those fateful Valentine's Day promos in New York that led to the existence of Lovely Kiss/Horn Drill Nidoking back in the GSC days. Or Eevee with Growth. Or Bubble Magikarp. The problem with all of this goodness is that because of the mandatory Shiny on the gerbils, their natures are locked in as well. And it's not known what nature that's going to be.
Basically, what this comes down to is this: If Raikou is stuck on something stupid like Bold, it's a stinkbomb waiting to happen.