Fox has been blasted in the past for their reality programming (Marry a Multimillionaire, Temptation Island, etc...), but they finally got it right with Small Town X.
Before I talk about what makes the show great, it does have some weak points. The players are not as interesting as the Survivor 2 bunch, and the game goes by without you even being able to remember some of their names. Also, you don't seen enough of the interactions between the players to understand their emotions towards each other.
But, the contestants are not what make this show interesting. Watching this show is like stepping inside a video game. There are several twisting plot lines to follow, and a number of clues and false leads to sort out. Due to these factors, X is more suited for audience involvement than the rest of the reality genre (with the possible exception of the Mole).
I hope that Fox runs something like this one again, perhaps with a different location or genre (X-Files style, anyone?)