Opal, the reading issue is gonna be almost impossible to beat. Unless they have something like Banjo-Kazooie for the PC I am out of ideas.
You’re going to have a hard time finding an RPG that doesn’t require lots of reading. RPGs by definition are heavy on story and since recorded dialog is expensive and written text is cheap, most RPGs use the latter to deliver their copious exposition.
Someone has already mentioned Pajama Sam. Virtually everything that Humongous does is very entertaining and kid friendly. http://www.humongous.com.
You might also check out Hype: The Time Quest from Ubisoft. It’s a Playmobil-branded game about a knight sucked through time by his evil nemesis. I haven’t played it but like all the Playmobil games it’s very light on reading.
I suggest the “Harry Potter and the Sorceror’s Stone” game. There are four: PC, Playstation, Game Boy, and Game Boy Advance. I’ve played the first three and the PC version is by far the best.
There isn’t much reading involved–it’s mostly puzzle-solving, hunting around for secret rooms, and occasional dexterity-type stuff like tracing spell patterns, running from things, and playing Quidditch. The only thing you need to read is the goals for each section–the rest of it is all characters talking to each other.
If he’s into Harry Potter at all he’ll love it.
Diablo is pretty easy for kids to understand, and most of it is voice acted. I’m trying to think of other ones that are currently available, but RPGs are generally very reading oriented.
Unfortunatly, I can’t come up with much for kids that isn’t on a Nintendo system. Pokemon is a great RPG for kids, even if it does inspire great material needs.
Maybe try one of the Harry Potter games, or something as such, until he’s able to read a bit more fluently, then go to something like Final Fantasy or it’s clones.
If he’s been bad this year, get him Pool of Radiance. All the bad rules of 3rd edition, with none of the cool things. I think even a 6 year old would get frustraited by it 
John
‘The Legend of Zelda: Ocarina of Time’ has some reading, but it’s not very intensive, 95% of the game is exploring and figuring out visual puzzles. If you are in the same room you’d only have to devote a half-minute or so every now and then to read it to him. It’s a Nintendo 64 game, but there are emulators available for free on the internet. To keep it legal you’d want to buy the cartridge before downloading it’s ROM, however.
I’m not sure how intuitive the controls would be with emulation, however, I’ve never played an N64 game that way before. It would be about perfect for what you describe, so it would probably be worth it to buy an N64 just for that game. You could probably get the system and the game used for less than $100 at Funcoland or somewhere similar, and I saw a copy of the game for $15 on EBay and the N64 with a few games for a little over $50.