I've only been back a handful of times, but my impression is that the "night life" is vastly overrated - expensive beyond all reason, unless you like $15-$20 cocktails and obscenely loud music. Broadway show tickets can run upwards of $200 apiece, though they can be had for considerably less.
On a nice day, you might check out Central Park and its zoo, and then up Fifth Avenue to the museums (the Guggenheim, the Metropolitan Museum of Art and the Museum of Natural History) or go downtown to Little Italy or for Asian food - the places can be crowded, but the food is often great and not outrageously priced. If you want to visit the World Trade Center memorial, you have to get tickets in advance (they're free, and available online).
Daily parking rates seem to be about $30-$35 these days, and then navigate the subway system or crosstown buses to get where you want to go. Definitely would not want to live there today - I'm not young or rich.
DC is better and that was first on our list. We have been to DC a couple of times and have enjoyed it.