Protagonist
A protagonist is the main character of a story. In gaming, the protagonist is the playable character. Some games give you a choice of protagonists, and this can either just change the character or alter which story path is followed.
Traditionally, a protagonist is the main figure of a piece of literature or drama and has the main part or role. Alternatively, the phrase denotes a primary advocate of or proponent for a cause or movement. The main character can be a hero or a villain in a story - it is just the character with the lead role. In literature, the protagonist is characterized by his/her ability to change or evolve.
It should be pointed out that the protagonist is not always the hero of the story, as implied in the Grand Theft Auto games. They may commit a crime of some sort, but he/she is still considered the lead character, and is known to help out his/her allies or close associates.
The protagonists of between Grand Theft Auto III and Grand Theft Auto IV share similar qualities. They are all new to town, either returning after spells away (such as Carl Johnson and Toni Cipriani) or have never been to the city before (such as Claude, Tommy Vercetti, Mike, Victor Vance and Niko Bellic). The protagonists usually start with nothing, with minimal influence and reputation, having to do odd jobs around, gaining friends (like Wu Zi Mu, Little Jacob, Asuka Kasen, and Kent Paul ) before moving up the social and ecomonical ladder. They eventually start doing real jobs and cutting real deals as their prominence, respect, and reputation begins to grow, until they end the game on top of the city, or at least with some powerful business and/or friends.
The opposite of a protagonist is an antagonist, which is the main person working against the protagonist. Again, this can be a villain or a hero, though usually a villain. The main antagonists of the Grand Theft Auto games are usually introduced very early in the story, usually the the protagonist's friend or acquaintance until a major betrayal (like Catalina, Sonny Forelli, Frank Tenpenny, and Dimitri Rascalov) and are usually seen, heard, or mentioned throughout the game, moving against the protagonists' plans or goals, until they are finally confronted in some big event by the protagonist at the end of the game.
Current list of GTA protagonists