Can You Get Rayquaza in PokéPark Wii? No — But It's in PokéPark 2

Rayquaza is not obtainable in PokéPark Wii: Pikachu's Adventure.

Legendary Pokémon Available in PokéPark Wii

• Mewtwo — Sky Garden (post-game).
• Lugia — Seafloor (post-game).
• Groudon — Fiery Mountain (post-game).
• Kyogre — Ocean Cavern (post-game).

Rayquaza Appearances in Other Games

• PokéPark 2: Wonders Beyond — Rayquaza is in this sequel (Wish Park area).
• Mainline games: Emerald, ORAS, Sword/Shield (CT), Scarlet/Violet (Indigo Disk).

If you want Rayquaza in a PokéPark game, play PokéPark 2: Wonders Beyond (Wii).