I appreciate the responses...each one is valid for his/her car and perspective. This is a tricky subject because everyone seems to have a strong opinion on it, its tough to find someone in the middle who has no preference.
The question was asked "Why not mod it"
For me (and I will recognize this as strictly my opinion) it takes away from the purest form of the vehicle as envisioned by the factory engineers. When I show my NSX at shows, I identify what parts are aftermarket (exhaust and cold air intake) and they respect the car for that. Sure an 07 Z06 can eat it's lunch, but the NSX is far superior (again my opinion) in regards to engineering. I don't feel the need to update it to match Z06 performance, cars of that performance range didn't exist when my 94 was built and, to me, its akin to comparing apples to oranges.
Is the stock NSX outclassed by many sports cars today, sure....but frankly I don't care. I'm currently in the market for a 1999 355 F1, and its already outclassed by vehicles which cost less. I'm buying it for what it is, a stunning Italian car with a great transmission.
NSXGMS brings up an excellent point and one which I can almost agree to, that the 2005 stock NSX was outclassed due to Honda's lack of R&D reinvestment in the platform. Even so, it is a great car and the end of Honda's dream of a supercar (for now).
Again, I recognize that I'm clearly in a minority here and think its great we have places such as Prime to discuss our differences of opinion.
At least we can agree that the NSX is a milestone in supercar design and engineering.