Before reserving a copy of the one video game title that may top Halo 3 in sales, I read up a little on some of the innovations that Grand Theft Auto 4 will bring to the series. There were three key aspects of gameplay in the series prior that were royal thorns in my side but are now addressed.
1) In a given Grand Theft Auto, when you've disobeyed the law in front of a police vehicle (beat up a pedestrian, run one over or shoot and rob them), the police would then try to apprehend you. The more crimes you did while the police chased you, the more aggresive their pursuit would become, which meant more cop cars would chase you, as well as a helicopter and maybe some reinforced F.B.I. vans if you were bad enough. The thing is, no matter what kind of twists and turns you did on a highway or in a residential area in your stolen car, you didn't have the ability to lose them. I always thought this an unrealistic aspect that took the fun out of the game a bit.
In GTA 4, a new radius system has implemented, so that the police's efforts can only be focused on you if you're in a certain proximity to them, thereby allowing a chance to get away.
2) The incentive to do missions was killed by the constant traveling between failed attempts and mission reception. I.e.: Say, I have to go to the city of San Fierro to talk to some corrupt lawyer who will pay me to take out a mafia member that's turned state evidence. I'd have to steal a car and travel all the way to the countryside, where he's hiding, to kill him (in addition to obtaining firearms somehow), which is (digital) miles and time away. When I get there and fail the mission (because he's killed me first or while driving I've fallen off a cliff or something), I have to once again obtain a vehicle and drive all the way back to San Fierro, so the lawyer can send me all the way back to the countryside, reobtaining weapons and losing money in the process.
In GTA 4, when you fail a mission, you can go to your cell phone (which will be an important staple in the game), option to restart the mission, and simply be replaced in San Fierro to start the mission again. Additionally, if I die, I'll wake up in the hospital $100 poorer, but with my weapons still intact. If I get arrested, the weapons will be confiscated.
3) The shooting controls and gameplay were awful. First, the target locking system might have been accurate for the most part, but it would constantly be stuck between targets that were far away while I tried to lock-on to someone that's standing right next to me, killing me. And life drained out of you pretty fast while being attacked, which you couldn't really stop by hiding because you were a sitting target no matter where you were.
In GTA 4, a new shoot-and-targeting system similar to Gears of War has been placed, giving you the ability to get into substantial cover and direct yourself properly towards certain targets.
I really look forward to this new installation, but see for yourself.