Yeah, I always get both games when they come out, one becomes my main game the other serves two purposes.
1) Gives me a chance to build another team (there are always too many pokemon that I want to use at the same time).
2) to provide the other with exclusives.
Currently my main game is Emerald. I recently rushed trough Sapphire to get Latias. When I'm playing a game I try to catch a couple of exclusive pokes and save them on pokemon box, that way I can transfer even if I can not trade e.g. if I then restart that game.