In fairness, the "last model" NSX was 2005, not 1991. In any case, let's look at the 911 from 1991 versus current.
I present two naturally aspirated, RWD, flat-six, rear engine, manual transmission cars. Remove the badges and any 12 year old will still say "Porsche 911."
I used a 91 NSX because at that time it was the sum of Honda's thinking on a mid-engined sports car.
As Bricks and bio has stated Honda didn't keep up the evolution of the car over the years so by 2005 it was essentially the same car, out of date, and out of compliance with current standards of the day.
The new NSX is the sum of Honda's thinking on a mid-engined sports car 25 years on.
A new design, a new method of construction, a new type of driveline.
Equally as much of a departure from the norm as the 91 NSX was in it's day.
And the philosophy seems about the same.
Superior handling, driver centered, high quality, many technical innovations, adequate power.
Not the fastest in the class in 91 nor 2016.
Yes Porsche has chosen to keep the family resemblance on the 911 which is astute of them given the long history of the 911 moniker.
Ferrari has chosen to move their design quite a bit from the 328 to the 458.
But under the skin of either one not much, if anything, has stayed the same.
I think those fortunate enough to own the NSX will be delighted with the car itself.
Not the marque with the most cachet, perhaps not the most endearing design, but I believe the car itself will be just a good or better than the 91 was in it's day.
Even the Lotus cars were deemed "Better Looking" and "Timeless" over the NSX. 
