An anomaly to me. It doesn't make sense. It is the largest train station in the world. It's one of the most gorgeous pieces of architect work and artwork in American history. It is a piece of art to walk through there. Yet it is only served by Metro-North Commuter Rail Road, the second largest commuter railroad in the nation. The first, Long Island Railroad, and not far behind New Jersey Transit, AND Amtrak ALL THREE operate out of Penn Station, a tiny basement under Madison Square Garden. Half of the tracks at Grand Central are empty. Why Amtrak was taken out of Grand Central is beyond me. The only reason Long Island Railroad and NJT aren't in there is because all tracks point north.
Grand Central has Metro-North Commuter Railroad, Subways (4)(5)(6)(7)(S), and lots and lots of shopping and food courts.