DS3 is really into robots/Transformers so he got DH the newest Transformers movie on Blu Ray. That will go nicely with the new PS3 that I got him since it plays the Blu Ray discs.
My son loves Mario Kart and they play that together frequently. Last year DS got DH the wheel accessory so they could play together (you don't NEED the wheel, you can just use the wii remote, but the wheel does make it easier and more fun).
I always try to pick something that they do together or is meaningful. It will be interesting once DS gets older and has more of an opinion.