First off, your old television isn't going to do this game any justice.  So fire up the big screen, crank up the surround sound, and piss off your neighbors/parents late into the night with this awesome next gen game.

The character development in this game is what really keeps you immersed in the story.  You are Nikko, a middle-easterny/russian badass who has come to Liberty City with the hopes of living the high life.  Your cousin, Roman, is your first contact as he shows you the city and introduces you to a few "friends".

Your ears will get a full dose of culture in this game as many characters have thick accents.  And even though (I think) Nikko sometimes sounds like Shrek, it all blends perfectly to make you really feel and experience the characters.

If you have the PS3 version of the game you will have the option to use the SIXAXIS motion control to reload weapons mid-fight, steer two-wheeled vehicles, boats, and helicopters; as well as other things I don't fully understand yet (you'll see), a pretty sick way to get around in my opinion.

The physics that are at work in GTA IV are every bit as realistic as in the real world.  If you run/sprint into someone on the sidewalk they will  lose their balance and fall, get into a high speed accident in a convertible and you will be ejected from the vehicle, try to stand atop a moving car and you will eventually fall, and easy on that handbrake 'cause your trunk lid is lethal to pedestrians.

Imagine a gaming world that bigger than either Vice City or San Andreas.  Now imagine no load times between any area in that world.  That is another great development GTA IV has masterfully created.  Walk, run, ride, drive or fly anywhere (there's a helicopter at the airport) and do so taking in the breathtaking views absolutely seamlessly (I didn't have any freezing issues on my PS3).

Aside from Liberty City being of colossal size, there are also many "activities" in which you and your friends can partake all around Liberty City.  Bowling, pool, darts, bars (don't drink and drive!), Cabaret shows, comedy clubs, strip joints (have a fifty handy!), and you can do all of this any time of day with any friend you haven't pissed off.

Even after all the gameplay I have attempted to vividly detail for you, you can't really get a good idea of how awesome this game is from an iReport.  You gotta see it, not read it.  So go out and buy the game, you won't be disappointed.