You got Articuno in your game , so that means you had...Froakie or Chestpin as a starter? I got Zapdos because my starter was Fennekin. It's like how it was in FR/LG, where the legendary that appears is supposed to be opposite the starter you pick. Like I picked Bulbasaur in LG, so Entei was the Johto Pokémon that I could hunt down. Well, in any case, the hunting gets a little annoying, but ultimately it leads to an encounter in the Sea Dragon's Cave off the coast of Coumarine City. It's like a reference to the second movie, where Lugia's revealed as the Kanto Trio's leader.
Anyways, yeah, I've spent a lot of time playing the games between the 3rd and 4th gens. I have almost all the games from Gen III onward, except for HeartGold (I only passed on it because I never got Gold version). I've played almost all of them through too, except White 2 and Y (both of which I'm still working to finish). I've amassed a huge collection in all my games, but I don't have a problem sharing the extras from the titles I've been planning to restart. Speaking of which, I'm halfway through Ruby finally and I just restarted Pokémon XD. I'm trying to get more extras from the Hoenn set so I have a little more bargaining power on the GTS for when I try to get some rare event legendaries that I couldn't get since I didn't have access to wifi at the time. It may sound a little obsessive, but I just like being on top of things like that, especially when I know not everyone's kept up with the series as much as I have.