The reason why 95% of people start learning the guitar, is because they want to be able to play songs. This is totally natural, since the point of playing an instrument is to make music. Only few people have set goals with the guitar, such as professional musicians or composers, but for most beginner guitarists, being able to play famous guitar songs will suffice.
Hence the big question, how long will it take before beginners can actually play the songs they like? The answer depends on several things, but mostly, how much practice time you can put into learning the guitar. The more you practice, the better you'll get, and the more you'll actually want to practice, since you'll have loads of fun playing new songs.