Sales or rental side? Manhattan or all five boroughs?
Sales inventory varies based on what price range, location and other specifics. Overall, there is a healthy mix of inventory, but be prepared to sacrifice on certain points. Even in the high end "uber" luxury segments of the market, just because you can afford a $20M penthouse, doesn't mean there s a gluttony of selections that meet all of your wants and needs.
Rental inventory is notoriously low as we are primarily, a city of renters. The vacancy rate is still well below 1% due to the never ending influx of new highers, students, transplants and such.
This varies greatly in the other boroughs aside from Manhattan. I only gave those stats as I assume you meant that when you said NYC as most people tend to assume NYC as only Manhattan.