Hrumph. Who are these people here? Are you TRQ? No? Then until he arrives, stand aside.
Shining Force. Specifically, 1, 2, and 3 (though good luck on the 3 front). 1 is out on the VC, and was remade on the GBA. Ignore the other Shining games. These started me off on SRPGs, though they're quite a bit easier than the Fire Emblems.
Front Mission. The DS has a remake of the fantastic Front Mission 1. Has a heavy emphasis on individual unit customization. If your son would get turned off by, say, choosing individual parts (left arm, right arm, torso, legs, right weapon, right shoulder, left weapon, etc.) for each and every character used, then pass. Myself, I like that stuff.
A shame that there's no Playstation in your house, as there's some very quality stuff on there.
FFTA definitely didn't do it for me, but I can't comment on FFTA2.
The Advancce Wars are made by Intelligent Systems, who also make the Fire Emblem games. They look quite similar to all the handheld FEs (which you should strongly consider getting if you haven't already, as well as the GC Fire Emblem which I'm guessing he's already played), though units are far more expendable and they aren't really RPGs.
Tactics Ogre on the GBA disappointed me, though some liked it. Hell, all those Ogre games disappointed me.
More as I think of 'em.