I've played and completed fable. Its not a proper sandbox game. Follows your normal RPG basic elements, quests, bosses, tournaments etc. Doubt he'll like it as he wants something very similar to GTA. Fun game though. The fighting system is basic but very easy to master. The system is similar to devil may cry. Graphics aren't amazing but still very easy on the eye for a slightly older game now and runs perfectly in any fight I found.
The whole gimmick of choosing your path of good or bad isn't as amazing as the game may suggest.