It depends on your version and preferences here are my advised teams for X and Y
(I have played through both versions)
X
Roserade
Lucario
Auroras
Blastoise/Charizard
Aegislash
Xerneas
Y
Roserade
Lucario
Tyrantrum
Venasaur/Blastoise
Florges
Yvetal
pokemon Y
Mewtwo is the best Pokemon in R/B/Y. No other Pokemon comes close.
For me, it would be any 6 starters know 4 different typesof movesExample:Greninja-BlizzardDark PulseWater ShurikenPower Up Punch
y-y-yes
Yes You Can Get A Pikachu In Pokemon X and Y.
If you mean best i would recomend pokemon x and y or any of the rumble games.
Pokemon X and Y are sold at MSRP of $39.99 (CAD)
The MSRP of Pokemon Y or X is $39.99 (CAD/USD)
Pokemon capable of learning Psywave as an Egg Move in Pokemon X and Y are Latios (Pokemon) and Gastly (Pokemon).
The Legendary Pokemon available in Pokemon X/Y are:Xerneas (X only)Yveltal (Y only)ArticunoZapdosMoltresMewtwoZygarde
718
YEs, you can get Xerneas in Pokémon Y but trading is required.