Good point.

The best place to visit (that has remained almost unchanged since the movie was filmed) is The Edison Hotel (241 West 47th Street, just off Broadway). You'll walk down the same hallway where Luca Brasi took his final steps and you'll enter the hotel's bar/restaurant that served as the bar in which Luca was killed. Look for the fish etchings on the door.

Its a nice example of art-deco style PLUS you can actually have a drink or two while visiting

Head east a few blocks to Sixth Avenue and 50th Street and see Radio City Music Hall (from which Mike and Kay exitted only to see the newpaper headline about Vito getting shot). You won't find the newsstand or the phone booth from which Mike called the mall but the marquee is exactly the same.

Take the subway downtown to the "Brooklyn Bridge" stop and you'll find see the courthouse steps used to film Barzini's final tumble (60 Centre Street). Some blocks west you'll find the Old St. Patrick's Cathedral at 263 Mulberry Street and you can go inside to see where the christening scenes were filmed for Part I.

Unfortunately most of the remaining film locations have changed drastically and are almost unrecognizable.