Unless he was 100% certain he could make an airport, he made the right decision. The entire flight lasted fives minutes, and I'd say he had only about 30 seconds to make a decision. Looking at the flight path, he probably could have made either Teterboro or LGA with about a mile to spare. But there was no instrument to tell him that.
Ultimately, everybody walked off the plane alive, therefore, he made the right decision.
The movie shows he landing tail first, not engines 1st.
Man would I like a couple of hours of dual instruction from this guy...
IMHO he, as you surmise, did make the correct decision.
Your calculation he could have made either aiport with a mile to spare could have ended up a mile to go after course corrections and maneuvering for runway alignment. When he made the 180 degree turn to return to the airport he lost a lot of altitude and that is the moment he knew either airport was not an option.
Speed and altitude are a pilots best friend and Sulley had neither. Bob Hoover used to put on an amazing air show exibition in an Aero Commander twin that is the best display of deadstick flying ever. He showed how altitude can be converted to energy (speed) and energy (speed) can be converted to altitude, neither of which Sulley had.
If you look at the flight path after the 180 degree turn you will notice he did not make any high angle turns costing him altitude but slight ones, preserving as much altitude as possible.
To land safely on a runway with the fuel on board would have required a gear down, flaps extended landing. With everything hanging out like that the drag would have been increased, slowing the plane even more and shortening the distance he would have been able to glide and possibly coming in short of the runway and ending in disaster. Everybody is alive, no break up, no explosion or fire. He did the best he could and what else matters?
He is a glider pilot and specificly says on the transcript that he couldn't make it to Teterboro. The river was his only option. I'm more than willing to accept his judgement in this case.