Is this a good pokemon team? Pokemon X and Y?

Yeah that's a decent team. I personally don't think Fan Rotom was the best choice. I would have gone with Heat or Wash Rotom. Anyway, I would get a Fairy-type Pokémon. Gardevoir and Florges are probably the best fairies in the game, but I would choose Gardevoir because it has Psychic STAB and it can mega evolve. Aegislash is also a great yet slightly OP Pokémon. Excellent for competitive battling with King's Shield, Swords Dance, Shadow Sneak, and Iron Head.

I would also make sure you have some pretty good moves too. DO NOT have more than two of the same type attacks. Like don't have a Charizard that knows Flamethrower, Fire Blast, AND Heat Wave. That is just silly and is one of the noobiest thing someone could do. It is also my biggest pet peeve in Pokémon. Here are the moves I would have your Pokémon learn.

Mismagius - Calm Mind, Thunder Wave, Shadow Ball, Psychic/Thunderbolt/Energy Ball

Torterra - Earthquake, Seed Bomb, Stone Edge/Sunny Day, Crunch/Synthesis (with Sunny Day)

Empoleon - Aqua Jet, Hyrdro Pump/Scald, Ice Beam, Grass Knot

Fan Rotom - Thunder Wave, Confuse Ray/Hex, Thunderbolt, Air Slash

Volcorona - Quiver Dance, Fire Blast, Bug Buzz, Psychic/Hurrican

for Gardevoir - Thunder Wave, Psychic, Moonblast, Thunderbolt.

Hope I helped!

I like your team but I would suggest to really think of your team that it really needs to be balanced in order to have a killing team especially in wifi battles :) choose pokemon that could defend other pokemon in your team that are strong and effective against the opponent. Your team is excellent but I'm seeing something that's being left which I don't know what it is cuzz I can't explain it myself lol but other than that good team

yes