Rewatched the Charizard/Greninja video slowly, here's who I saw come out of the poké balls. (All attacks of returning Pokémon are assumed to be the same as past games)

-Dedenne (Discharge in X shape)
-Bellossom (Sleep Powder)
-Chespin (???, my guess is Pin Missile)
--Snivy (???, my guess is Leaf Tornado, replaces Chikorita's Razor Leaf)
-Oshawott (???, my guess is replaces Piplup with the same Surf atttack)
-Staryu (Swift)
-Goldeen (Splash, should be Magikarp imo)
-Eevee (Tackle, further explanation below)
-Togepi (Metronome)
-Swirlix (???, not sure on this one)
-Metagross (Earthquake)
-Darkrai (Dark Void)
-Meowth (Payday)
-Electrode (Self-Destruct/Explosion)
-Entei (Fire Spin)
-Palkia (Spacial Rend)
-Gardevoir (Reflect)
-Latias/Latios (Steel Wing)
-Kyogre (Hydro Pump)
-Gogoat (???, looks to be Headbutt and is rideable)
-Zoroark (???, my guess is it uses Illusion in some way)
-Snorlax (Body Slam)
-Giratina (???, my guess is Shadow Force)
-Kyurem (Glaciate, could see it transforming into B-Kyurem or W-Kyurem and using Ice Burn/Fusion Flare or Freeze Shock/Fusion Bolt)
-Lugia (Aeroblast)
-Suicune (Aurora Beam)
-Deoxys [Attack] (Hyper Beam)
-Meloetta (???, looks like it could be Relic Song, maybe it transforms into Pirouette Form)
-Keldeo [Resolute] (Secret Sword)
-Victini (???, possibly drops music or other item like other Cute Legendaries)
-Spewpa (???, my guess is it uses String Shot and slows down enemies it hits)
-Fennekin (Ember)
-Inkay (???, my guess is it will ink the screen like Bloopers in Mario Kart)

Other Pokémon confirmed but not in the Charizard/Greninja trailer...
-Mew (same as Brawl assumedly)
-Arceus (Judgement)
-Xerneas (Geomancy, unsure of what it does yet)

Eevee Speculation- I hope Eevee does what he was going to before he was cut from Brawl, when he releases he randomly evolves into 1 of the 8 Eeveelutions and does an attack according to their type, or he just tackles as Eevee (as seen in the Direct video) or maybe tackle then evolve.