Ever since Gen 3, Rayquaza has appeared in every single anime Generation

Gen 3: Movie: Destiny Deoxys
Gen 4: Episodes: Malice in Wonderland! , Where No Togepi Has Gone Before!
Gen 5: Special: Iris vs Clair
Gen 6: Special: Mega Evolution ~Act II~ , Movie: Hoopa and the Clash of Ages
Gen 7: Episode: Showering the World with Love!

Isn't that quite interesting?