It depends what type of food he likes but I think the 50's Prime Time Cafe in Hollywood Studios is fun and they are great for Birthdays. It also depends if he wants any attention drawn to him - O'hana would also be fun.
Can you throw out any more details about his likes/dislikes, does he seem too old for character dinners, has he been to disney before, are you going to WDW or Disneyland, which park is his favorite, etc....
We are doing the Spirit of Aloha Luau for my daughter's 16th Brithday in September. She has never been there and thought it would be a great adventure. I think the dinner shows are a great idea, because you get a meal and a show which makes it an event and they usually acknowledge people's birthdays and anniversaries during the show, making it lots of fun!