It has poor graphics with insane requirements. For example GRID - great graphics with friendly requirements, but here... :shadedshu
I will wait for some patches and hope they'll optimize the game.
You have to consider what is going on in the game. You can't simply say it doesn't look as pretty as other games, so it has poor graphics. The number of textures, NPCs, cars, and buildings in GTA:IV is huge, no other PC game probably even comes close to how much is going on. Yes, everything in the game doesn't look as good as it might look in other games, however other games don't have as much stuff in them. The more stuff in the game, the less detailed everything has to be. It isn't like Crysis, where you might have
maybe 3 vehicles being rendered at once, and
maybe 5 NPCs. You can stand still and look around in GTA:IV and see 15+ vehicles all being rendered, and 30-40 NPCs. That is a lot to render, of course it isn't going to nearly as detailed. But, IMO, considering the number of things being rendered, they are pretty damn detailed. Each has semi-realistic damage characteristics, and they do look like cars and people.