The question is, what to run for him,
So, in people's opinion, is 4e compatible a good system to start a 10 year old on?
How about the Star Wars Saga Edition?
Or, should I just break out the OD&D red box and the crayoned dice, and sic them on Bargle?
For what it is worth, I suspect my twelve year old might like 4e but my 11 year old son, who is perhaps the most avid gamer of the four, is quite vocal in his disdain for aspects of the new edition.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.