It depends on what you're reading. I think watching an insightful documentary about history, science, etc. is the same as reading an insightful book, either fiction or non-fiction.
Therefore, watching un-insightful TV (ie. reality shows, sitcoms, etc.) is the same as reading a un-insightful book. It all depends on the content and educational factor.
Then, there's the question of how much un-insightful TV or reading do you need to do to be considered a couch potato...hmmm, it's all relative. If you consider yourself a couch potato if you watch 10 hours of TV, and you watch 10 hours of TV, then you're a couch potato. However, if you consider yourself a couch potato if you watch 30 minutes of TV, and you watch 30 minutes of TV, then you're a couch potato.
In my opinion, it all depends on the content.
~Sarah