The original rocksmith was more of a crossover of guitar hero with a real guitar. The second version is more teaching and practice than game. Both versions will teach someone who has never picked up the guitar how to play but the second one is more useful for those that know how to play.
I have a few success stories with rocksmirh and teaching people the guitar. I picked up an epi LP for a mini rocksmith festival where my big bro's kids competed for the LP. His son, that had never taken a guitar lesson but a big gamer almost won. His daughter who had quite a few lessons but doesn't like video games barely won. It was blast! Funny thing is his son now has the epi, and I don't think his daughter still plays...