Do I buy what he wants for Christmas?

My 5 year old son Michael has a very clear idea of what he wants for Christmas. It is called the Pokemon Tower, and looks like this. He has a number of small Pokemon plastic figures, and idea seems to be to play with the figures on this Tower. In spite of our efforts to talk him out of it (why not make something with Legos?), he continues to insist that this is the only thing he really wants for Christmas. He is even working hard to put together a letter to Santa to ask for it. Apparently other kids at his preschool have it too, and he just needs to get it.

Right now, I'm thinking No way! He'll get bored with it and it will end up in a corner of the room taking up space we don't have in our apartment. But, at the same time, he seems to be getting his hopes up about the whole commercialized Christmas myth: If he is a good boy, his wish will come true. Do we grant it and keep his hopes in the magic of Christmas? Or, do we buy something sensible...