Well, I say you work them from up to down.
My personal favorite is my Pokemon Emerald. I used to have every event on it and I was able to catch alot of legendaries by muxing data to my games that had the events on it. Plus, you can catch all 3 of the weather group, Rayquaza (which can be caught after you save the city with the final gym from Kyogre and Groudon instead of after the elite four challenge in Ruby and Sapphire in the same place you found it), Kyogre (found after battling/catching Groudon and found by the place where you get Castform), and Groudon (first pokemon being able to found after the elite four challenge, same as Kyogre).
I own all of those games.
Plus - You can get the Johto starters in Emerald by seeing 200 pokemon in the Honneh pokedex.