I like your team however there are a few changes that need to be made:
Firstly; pick between Charizard and Talonflame. They're the same types (although Charizard X is fire-dragon type). They're still essentially the same. I have two teams; one in which I use Charizard X and in the other I use Talonflame. (I prefer Talonflame because of his speed, Gale Wings ability and Brave Bird move).
Right, on to your Pokemon:
Good, I like him, I use him a lot too. EV's, nature and item = good. However, I suggest the following moveset (if you're planning to use this team for double battles):
- Mat Block
- Hydro Pump
- Dark Pulse
- Ice Beam / U-Turn
Mat Block protects both Greninja and your other Pokemon from any damaging attacks that your opponent might use for the first turn only. Meaning that if you start with Greninja + other Pokemon (such as Charizard / Talonflam) and you use Mat Block, then you can use Swords Dance on Charizard / Talonflame straight out without risk of getting wounded. Or you could use this as an opportunity to get a free attack in first without being wounded. Mat Block is just awesome to start with especially if you use a Speed EV trained Greninja. The other moves are self-explanatory; such as Dark Pulse; it covers your Dark weakness, plus along with Greninja's Protean Ability it makes it a beast move for Greninja.
Mega Charizard X
Beast. Great moveset except I would switch Dragon Dance for Swords Dance purely because it increases attack by 2 instead of just 1. However, if it's the speed you want on Charizard then use Dragon Dance. Although, Mega Charizard X has the ability Tough Claws so maybe switch that Outrage for a Dragon Claw. Possibly get an Earthquake in there as well because of Mega Charizard X's high base attack.
I've never used Electric-Type Pokemon in my competitive battling so I can't comment on him. I can only suggest to possibly switch the Wild Charge with Thunderbolt. Purely because of the recoil.
Right, here you have to make your decision; Mega Charizard X or Talonflame? Here's my Talonflame:
Talonflame (M) @ Leftovers
Ability: Gale Wings
EVs: 252 Spd / 252 Atk / 4 HP
- Brave Bird
- Swords Dance
- Flare Blitz
Very similar only I got rid of Roost and gave him Leftovers instead of Citrus Berry. Plus I use Greninja Mat Block + Talonflame Swords Dance to open up. This gives me a beast Talonflame with huge attack to start off with. Then I sweep with Brave Bird, letting the Leftovers heal him when needed. If I come across a team with Pokemon that may have greater speed; I start off with Greninja Mat Block + Talonflame Tail Wind to give my team a speed advantage.
Gengar (M) @ Gengarite
EVs: 252 Spd / 252 SAtk / 4 HP
- Shadow Ball
- Energy Ball
- Giga Drain
Note: Mega Gengar isn't an official OU Pokémon so my Gengar wouldn't count. Only use it for moveset suggestions.
It really throws my opponents off because they don't expect my Gengar to have 2 Grass-Type moves that cover my Ground/Rock/Water weakness. Nor do they expect him to have Thunderbolt which covers my Flying/Water weakness. It's a weird moveset for Gengar, I know, but it works for me.
But your Gengar is really good too though.
Nice. Possibly get a Dark-Type move in there if you don't get Dark Pulse for Greninja. I personally use Garchomp however, Tyranitar is a really good decision.
There you have it. Hopefully this advice is good. Take from it what you will. I suggest switching your Mega Charizard X for a Psychic- or Fairy-Type to patch some type weaknesses. Maybe Metagross. Here's mine:
Metagross @ Assault Vest
Ability: Clear Body
EVs: 252 Spd / 252 Atk / 4 SDef
- Meteor Mash
He works really well with Talonflame or Gengar.
Please let me know if you agree or disagree. Maybe even check out my teams (I've asked two questions on the "Rate My Team" section - One with the Mega Charizard X, the other with the Talonflame).