Good but not as great as the hype
First things first, this is a very good game with nice graphics, a decent soundtrack and realism but Rockstar has made the game too realistic for its own good and as a result has lost some of its GTA zing. Part of the fun in playing the previous titles was the crazy vehicles and free roaming which have been really toned down which has come as a shock to many including myself after playing San Andreas. Most of GTA iV you are confined to the streets seeing the same boring style of buildings which can make the game feel one dimensional, the only respite being the helicopters which can be fun flying in and out of the buildings but that gets old fast. Speaking of helicopters the only outlandish vehicle reminiscent of past titles is the attack chopper which features machine guns, besides that the vehicles are average and after a while travelling the city becomes a chore that the taxi's are a god send.
Some other features that were not included since San Andreas are car customisation much to the dismay of many, while not essential to the game it is a nice touch. Just like the more clothing choice and the RPG elements no longer present.
The great thing people loved about other GTA games was the completely ridiculous and over the top missions like stealing a jet pack from a secret government base in the desert. The missions in GTA IV are repetitive with only a handful of over 90 missions actually standing out as really enjoyable, notably "Three Leaf Clover", the majority being kill someone or follow someone then kill them.
I think this game became way over hyped which has let many down. This has left an opening for Grand Theft Auto's rivals, notably Saints Row 2 (released later this year), which claimed by many to be a GTA clone, has retained the appeal that the previous games in the series possessed.