He was turned on to super heros at a very early age by cartoons and movies. And ever since he learned to read, his main interests were super heros and villains. Especially the villains. He knew of my comic collection but also knew he wouldn't live to see 6 if he ever touched any of my comics, so he asked if I would read some to him.
I started with TBPs so he'd get the entire story. He's very mature for his age, so I wasn't concerned with reading the main titles with him (as opposed to restricting him to kids stuff). Around this time, the local newspaper started including entire reprint books of Amazing Spider-Man with the Sunday edition, so those were the first comic books that he owned himself. I told him that if he could take care of them, I'd start buying him more. He took care of them, and I held up my end of the bargain. He started with the kids section, but now dabbles in both the kids and the main sections, but primarliy the main section now.
Now he's 8 and has his own allowance, so the lid has been blown off the whole comics thing. I think he was the youngest kid at the LCS with a pull list until he realized he could save money by subscribing through the publisher.
Sorry for the long-winded answer, but you asked.
Sounds like you have a pretty intelligent kid on your hands 
