Welcome to the forums!
I've moved this post as a separate thread from the do you think Pokémon like Diglett, Bellossom, and Jynx have feet? thread over to Pokémon Gaming Central. In the future, please remember to stay on-topic and if you want to discuss something else then you can either make a new thread or find a thread that discusses it. Thank you!
As for the topic, there's a fair number of legendary themes I personally enjoy; Ho-Oh, Rayquaza, Reshiram and Zekrom, Xerneas and Yveltal, and Necrozma. If I had to pick one, it would probably be Xerneas and Yveltal, there's this epic energy overall as the entrance draws you into what the legendaries are like.