GTA4 fundamentally resolves down to the basic mechanics the first incarnations pioneered - stealing cars, shooting gangsters/cops, and completing missions. The fourth main installment of the franchise refines and improves many of these fundamentals. Most notably is the change to the gun shooting mechanics, where before auto-aim played a very large role and often times frustrated players, GTA4 uses an over-the-shoulder view similar to that in Gears of War. Also similar to Gears of War is the inclusion of a cover system that lets Niko hide behind objects to avoid getting hit. Hand-to-Hand combat has also been refined with a deeper moveset, and more combos available.
Driving has taken on a more realistic feel to match the rest of the game's setting. Cars now have more distinctive weights and features that sometimes make them more difficult to drive than in previous games. Vehicles that can be driven by Niko include cars, trucks, motorcycles, boats and helicopters. Bicycles and airplanes introduced in San Andreas don't make the cut.
Rockstar is taking the game back to its roots and placing the setting in the fictitious Liberty City. This time around the city is far more realized and offers a more than passing resemblance to New York City. Four of the Five burroughs are found in the game under fictitious names, with the notable exception of Long Island. Rockstar has been quoted as saying the city is smaller than the one in GTA:San Andreas, however its far denser, making the overall amount of places you can travel to be equal. Buildings are more interactive with many containing full interiors.
Grand Theft Auto 4 is the first time that online multiplayer is available to console players. Rock Star has taken cues from other modern online games and added their own GTA twist. Up to 16 players can take part in online matches that exist within the same open world of the single player. This means you can engage in one of the 16 different multiplayer modes and still travel to any part of the map, engage with civilians and do everything you can do in the regular game. Rock Star attempts to keep the interactions localized by making health and weapon respawns occur in select parts of the map.
Customization plays a large role in the multiplayer modes. Hosts are given the ability to specify the number of pedestrians available, cars in the streets, if cops are active, auto-aim settings, etc. Players themselves can also customize their digital personas with different clothing and body shape choices, the more you play, the more points you gain to unlock further customizations for your avatar.
Rock Star Social Club
Taking inspiration from Halo 3 Rock Star has a website that accompanies the game to provide statistics, community organization and other benefits to gamers. Not only do online games get logged in the social club, but extensive leaderboards and challenges for the single player game.
Differences between Xbox 360 and PS3 versions
Downloadable episodic content will be available exclusively for the Xbox 360 version. Any exclusive content/features for the PS3 version has not been announced yet.