Usually, I immediately buy the games on the release date :) But, if there is an awesome pre-order giveaway, I pre-order the games so I'll receive them on the day of release and with a neat collection item as well!
(i.e. with Pokemon X and Y almost a year ago, I received a Pokeball case for DS games, and with ORAS, I will receive a Tin-gamecase because I live in Europe, pretty neat!)