HCBailly and NakaTeleeli are my two favorite LPers.
HCBailly is an RPG fan who actually lives in the same state as me. He's pretty dedicated to showing as much an RPG can offer (within reason). He even beat Yiazmat in FF12. He had a save from his test runs that he used instead of doing all of that grinding over again, and he skipped 90% of the fight because it was basically the same thing for like... three hours.
He, and everyone else I've known, are unhappy about that fight.
NakaTeleeli is more widespread. Naka does a range of games, some of them fangames from Japan (generally fangames for Touhou) and let me tell you, he is smart. During his Okami Let's Play, he took the time to research and explain every single character's importance to Japanese mythology, as well as their symbolism.
In his Persona 4 Let's Play (which he did with his best friend ElementalOgre, who can be said to be something of a red oni to Naka's blue oni) he took the time to explain the symbolism present within each Shadow fight.
And in Persona 3, he's been explaining (in the description) the symbolism of each of the Full Moon Shadows, and how they relate to the inverse of the arcana they represent (that is, the Priestess Shadow actually matches the meanings associated with an inverse Priestess card)
Basically, he's smart because he does his research. And he does Let's Plays and stuff while having a job, too, so yeah.