Here's a tip to beat the games quickly, so you can catch pokemon that appear after the games (e.g. Latios and Latias) and access the new areas (Battle Frontier, etc.)
This works best with a Blaziken in my opinion, as it can beat two of the elite 4 effectively.
You need to get a torchic, get through the game until you reach Petalburg, and trade that Torchic over to another game (that's perferably already finished past the elite 4.) Train it up in the other game, and trade back to the original. Because the OT remains the same, the Torchic (which might be a Lv.60 Blaziken by now) will be at a high level, and it will obey you.
So, with a high level pokemon that'll obey you, you should be able to finish the game in twelve hours.
This works best with a Blaziken in my opinion, as it can beat two of the elite 4 effectively.
You need to get a torchic, get through the game until you reach Petalburg, and trade that Torchic over to another game (that's perferably already finished past the elite 4.) Train it up in the other game, and trade back to the original. Because the OT remains the same, the Torchic (which might be a Lv.60 Blaziken by now) will be at a high level, and it will obey you.
So, with a high level pokemon that'll obey you, you should be able to finish the game in twelve hours.