Going to get my 7 year old brother into Video Games. I wan't him to start with one of these 3 games.

My little brother has always watched me play games that I let him watch me play, but now I think he has done enough watching. I think he should join the Playstation Family.I want to get him started on the big three of the PS2 era. The only games he has watched me play are Skate 2 and Playstation All-Stars. When he isn't watching me I play BFBC2, Metal Gear Solid 3, Dragons Dogma, Uncharted 3, and Demons Souls. I never allowed him to watch me play anything that was too mature for his age because I didn't want him growing up with shit taste in games (In other words I don't want him to be one of those kids on CoD). He has recently asked me a few questions when I was playing PSASBR story mode of these three characters, "Who is that grey man with blue hat? Why does he steal from people?". When he saw the Jak v Ratchet scene he asked "Why did they wanna fight each other?" I want him to start with one of these 3 platformers, which do I start him on? I have only played Sly and Ratchet & Clank so I have no idea about the Jak series. He doesn't have much of an attention span so collectibles will make him bored I think. So Reddit, I ask again, which one Jak, Sly, or Ratchet?