GTA was a revolution due to the theme and the role you had to play: a robber trying to go up in the scale and become one of the bosses of the gangs int eh city: Liberty City.
You'll experience all the excitement of robbing cars and motorbikes, completing missions sent you out by the crime bosses, all this in a 2D top down view.
The local crime bosses send you out on missions ranging from carjacking to kidnapping to drug running. The more missions you complete successfully, the longer you retain and/or advance your criminal status, because your goal is to become one of those bosses.
Now Rockstar has decided to give it free of charge. Its amazing how a game that is more than 11 years old can surprise you. Don't hesitate, download GTA for free, choose the character you like the most and get into this irreverent gang story.