When the series began, I thought it was Articuno, as I didn't know what Articuno looked like until after the episode (of course, Ash's observation in the following episode of the mural of the Legendary Pokes rather gelled this theory for me).
Once I saw Ho-Oh, I knew for sure. So yeah, it's Ho-Oh. They do show that scene as part of the original Pokerap.
Ho-Oh appeared again at the end of the series, as Ash was heading to Hoenn.
So there is your answer.