Little unique features like this are common in games, but Guild Wars is the only one that does anything for the birthday of the character or the player to the best of my knowledge. And it's such a little thing that it seems almost strange that more games haven't copied the idea. Of course, it requires tracking date of creation for every single character and it can lead to some issue (some of the birthday presents in GW wound up with exorbitant prices on the secondary market).
So what do you think? Would you like to see more games marking your character birthdays? Or do you think it's a cute idea that doesn't need to be revisited?