Is the NYC CityPASS a good deal?

It can save you a few bucks, but it's probably not nearly as good a deal for you as they claim (note that there are other similar passes with different offers as well, those should be evaluated separately).

The CityPASS folks promise 40% savings, which sounds pretty good, but there are some caveats. Significantly, that two of the included attractions (the Met and the Museum of Natural History) are pay-as-you-wish, and many visitors do not pay the "recommended donation" amounts (the average Met visitor pays $11, which includes people who pay the full price not knowing about this policy). What you pay is up to you, but it's reasonable to assume CityPASS isn't paying the Met and the Natural History Museum anywhere near the full "recommended" donation amounts for their visitors either.

So, what's included? (All prices are for the adult pass, some attractions have senior discounts that would make the CityPASS a worse deal if you qualify. I'm also assuming you're not taking advantage of any free museum days, which can further reduce your costs significantly. I further assume you aren't using any of the coupons which can be found online for some attractions.):

• The Empire State Building, 86th floor observatory + same night readmission. CityPASS values this at $47. ESB standard admission is $32 without the same night readmission, which is probably good enough for most people.
• American Museum of Natural History. CityPASS values this at $27, which includes a Planetarium or Giant Screen show. Admission is pay-as-you-wish for the museum, but you do need to pay $25 for the optional show.
• Metropolitan Museum of Art. CityPASS values this at $25. Admission to the entire museum is pay-as-you-wish.
• Top of the Rock or Guggenheim Museum. I'm not quite sure why you'd do both the Top of the Rock and the Empire State Building, since both are observation decks, unless you really hate art. The Guggenheim is normally $25, reduced to $15 when parts of the museum are closed while exhibitions are being changed.
• Statue of Liberty & Ellis Island or Circle Line Sightseeing Cruises. The Statue + Ellis Island is worth $18, but the CityPASS ticket won't let you go inside the statue; that requires a separate ticket and advance reservations. The Circle Line Landmark Cruise does cost $37, but there are other Circle Line cruises that cost less, not to mention other boat tour operators.
• 9/11 Memorial & Museum or Intrepid Sea, Air & Space Museum. The 9/11 memorial is free, but for the museum, the official website says it costs $24, not the $26 CityPASS claims. At the Intrepid, the CityPASS won't get you into the Space Shuttle Pavilion, which requires a $33 ticket instead of the $26 one.

Where does that leave us? The adult CityPASS costs $116. A few logical combinations:

• ESB + Natural History + Met + Guggenheim + Circle Line Landmark Cruise + 9/11 Museum = $128, if we give the Met and the Natural History museum $5 each. $12 savings (9%). Adjust up/down based on your desire to donate to these museums. Give them each a dollar and it becomes a $4 savings. Choose a cheaper cruise and the pass becomes a loss.
• ESB + Natural History + Met + Guggenheim + Statue of Liberty & Ellis Island + Intrepid = $109 with $5 donations to each museum. You've wasted $9 on the pass (or give the museums a few more bucks and call it a draw).
• On the other hand, you can come out ahead by a few bucks if you want to see the Space Show or a giant film at the Natural History Museum.

Therefore, the CityPASS can be marginally worthwhile if you already want to do the most expensive options from the choices, at the expense of locking you into specific things you must visit to get any benefit at all. You also give up some ability to buy upgrades to certain attractions by using your pass, such as access to the inside of the Statue of Liberty (though reservations sell out very early for this).

And the other downside is that the CityPASS locks you into a certain set of attractions that may not be the best use of your time as a visitor to New York, depending on what you want to see. Time spent waiting in line to go up two observation decks to get your money's worth or doing other touristy things may be better used for other things, some of which are free, such as going to a deli or brunch, visiting MoMA, seeing a play (they have those without singing you know?), venturing into Brooklyn or Harlem or another area more interesting than Midtown, chowing down at a food hall or Smorgasburg, walking the High Line, a bridge, or Central Park, or standing in the middle of Grand Central. Doing these sorts of things, or whatever interests you, can give you a far better feel for the city than running from one tourist attraction to another with a determination to get your money's worth.

And, of course, if you want to and are able to support the museums by donating more, that's always appreciated too.