4e is aggressively simplified, generic Tolkien-ripoff fantasy tweaked for moral-black-and-white and designed to encourage party harmony and ease of play. I can't think of a better system that a 10 year old kid would leap towards, honestly.
Hmm... I suppose that not being rules-light might be a big deal, though. But I guess that I don't really know a lot of really simple RPGs (and the ones that I do know I don't like very much due to the concessions that come along with it.) And nostalgia for the DM along with the kid slaughtering orcs and goblins and dragons by the score is going to be best fulfilled in Dungeons and Dragons, albeit it's an edition with a shifted focus.
I'd agree that DnD4e isn't the top choice of first RPGs in general, though. It certainly doesn't encourage the RP part of RPGs in the actual rules.