First off, Ive not found much of a performance difference between 993TTs and MY 02 NSX (when it was stock).
There is a huge difference between a 993TT and the nsx, even compared to a turbocharged nsx, I think my 993TT was faster; I assure you its faster than your '02 nsx.
The conversation is dissolving (rather quickly I might add) from a discussion about the GT-R, into a comparison between two cars which have nothing to do with the topic, a 1980's entry-level porsche, and the designed-in-1988 Honda nsx - neither of these cars can (or should) be compared to the released-in-2008 Nissan GT-R, as it has 20 years of ingenuity behind it, it would be like comparing the 'new' nsx, when it was released, to a car from the 1960's - nsx spanks porsche 356? Who wants to read that story?
As for the 951/nsx comparison... the nsx is a faster car, I have driven a 944 turbo, and came away underwelmed... perhaps its my bias against waterpumpers, but 217hp pushing 3040lbs around, with a vintage turbocharged system producing the powerband, doesn't make for a very entertaining drive. The nsx has a greater power/weight ratio than the 951, but they're cars from different decades, and a comparison is unfair. The saving grace of the 944 turbo's continued existance is club racing, people snag a cheap 951, strip it out, race the crap out of it, blow up an engine, throw another one in, and keep going - I remember PCA track days with 951's running insane levels of boost, fully prepped, keeping up with newer cars - this does not make it a better car, only a good platform from which to base a race car. The miata is also a good platform from which to base a race car, does that make it exotic, or well-suited towards street driving?
The nsx has 20 years of Japanese aftermarket behind it, which ensures we will be able to screw with them for many years to come - it is a platform, however, which is becoming quickly dated with new 400hp-500hp-600hp+ cars coming out every few months, there is only so much 270/290hp will do. Various suspension band aids, turbocharger band aids, etc. can be applied, but then you have a car that perhaps matches the performance of newer offerings, or slightly exceeds it, wrapped around in a 10 year old interior, with stiff suspension and a loud exhaust. The nsx is a great car, its reliable, but it is a car of the 1990's, just as the 951 is a car of the 1980's, and the GT-R is a car of 2008 - there is no escaping this fact.
There is also no denying the fact that a good-condition nsx is a great package, its enjoyable to drive, and has an aesthetic appeal far beyond what its age might suggest. There is a reason the resale values of nsx and 951 are disproportionate, and its not because of magazine articles published in the early 1990's.
