|Houou: Japanese houou, "phoenix"||Ho-oh: from the Japanese name "houou", Americanized|
Game Boy Games: Gold/Silver/Crystal
Getting your hands on Ho-oh takes a while, depending on what game you have. If you have Gold, you meet him at level 40, after getting the Rainbow Wing by saving the Radio Station in Goldenrod. In Silver, you have to get to Pewter and talk to a old guy on the street, and then he'll be at level 70.
In Crystal, it's a long task to get to Ho-oh. First you have to beat the Elite Four (Actually, the Elite Five) and then you have to catch Entei, Raikou, and Suicune. And no trading, bitch. It has to be the ones from Crystal. The Game knows. Catching Entei and Raikou mean running around like a moron--again--but Suicune will be in one little spot. You get her with the Clear Bell, a Gift from the Radio Director in place of the Rainbow Wing/Silver Wing. Then you have to go to Ecruteak, ring the bell so the Monk lets you by, then you get jumped by three monks and have to battle them, and then you can finally get to Suicune. And then you have to catch her and not kill her. At least she waits for you.
Either way, you're gonna climb to the top of the Tin Tower, and he'll be sitting on the roof waiting for your ass. He'll be at level 60. You can't even get into the Tin Tower without the Rainbow Wing, mind you, and the monks won't hand it over till you have three Beasts. After a long and complex path to the top, you get to the roof where he waits. Save before you touch him! Stock up on a lot of Ultra Balls and the like, or use your Master Ball. He'll keep healing himself until you tire him out, and the best thing to do is chip away at his health and then toss balls at him.
Ho-oh is the only creature to learn Sacred Fire, but that's only if you get to him at level 40. He will have Recover though, a move that's annoying when you're on the other side of it.
Game Boy Advance: Ruby/Sapphire/Colosseum/FireRed/LeafGreen
One legend, one game. Somewhat. Anyways, no. Not in Ruby/Sapphire. But you can get one in Colosseum once you catch and purify all the Shadow Pokémon, or beat the 100 Man Battle Challenge. Have fun. =P I'm just purifying things. Much easier. They use Pressure as well--2 PP per move. Boy, we just have Pokémon wetting themselves everywhere, man.
Ho-oh was thought to be the legend of Psychic long ago. Now we know that's Lugia. Now we all know he's fiery and fun. But I still think that there are better Fires out there. At least he doesn't look like a chicken.