Being of the most popular franchises in Japan, it comes as no surprise that some effort is put into the advertising for commercials. I thought I'd highlight a few, and also list some of the odder ones. (Sorry, I didn't see many videos with translations.)
Dragon Quest VI Ad (featuring cos-playing)
Dragon Quest IX Ad - This one is American, featuring Seth Green
Dragon Quest V Making of Advertisement - The Cosplay might look silly, but you can see its not shabbily put together. Click here for the finished advertisement.