You're all talking about real life comparisons about Liberty City and New York...but hey, I don't think that's the answer to correctly lay out a map.
One of the known cities in GTA 4 is Liberty City -- NOT New York. It's important that we know this, and keep this in mind. Liberty City's most actual version is the one from GTA 3 (with some details from Liberty City Stories). So, with this version in mind, I made a map, with GTA3's Liberty City as a point of reference.http://img394.images...ymapgta4wd2.jpg
If you can't understand the images, try downloading the image and zooming in.
And please note that all of that locations are suppositions based on the trailer and on GTA3's Liberty City.