My son's 7th Birthday was last month, and his Grandparents got him Castle Panic. We (including his Mom!) have played this game at least twice a week since then. It is a collaborative fantasy boardgame and it is awesome. It has a card driven mechanic where Monsters advance on your walls, and you work with the other players to wide them out before they destroy your castle. The tokens and 3D walls are very appealing to the boy and the 'record keeping' is just complex enough to keep it interesting for the older folks. I have already started working on a plan to convert it to a miniatures game.
Did I mention it is collaborative? The boy and I really enjoy the fact we aren't trying to trounce each other. He is still at that age where "let's fight pretend enemies" is still more fun than competing head-to-head. I should do a more in-depth review, but you should just check out the link above or Wil Wheaton's Tabletop episode featuring it.