Why are so many great sports cars built in Italy and not, for example, in Spain?

This may not have anything to do with automobiles, per se, but may be related to the characteristics of Italian industry. Italy has an unusually high percentage of small businesses. It is far more common to be employed in a small company, particularly those with fewer than 100 employees, than with a large corporation. This does not mean that large, trans-national corporations do not exist. Quite the opposite: Fiat, for example. But it does means that there is a high probablility that there are a greater number of companies producing any one specific product. Since speciality automobile manufacturers tend to be fairly small, compared with the Fiats and General Motors of the world, there may simply be more of them in Italy per capita than one would expect to find elsewhere. As to the cars being great, that is a personal judgement. But there is also a tendency in Italy towards the production of limited numbers of highly refined products, particularly specialty items. This is another byproduct of the small company orientation: one or two key people driving a small, focussed company with the focus on craft, rather than production quantity.

I think that this question is based on false presumptions. Here is a list of great sports cars from places other than Italy, right off the top of my head:
Saleen S7, Ford GT40 (US) TVR, Aston Martin, certain Jaguars (Britain) Porsche, certain Mercedes and BMWs (Germany) Acura NSX, (Japan)
Last I checked, the Bugatti Veyron wasn'y Italian either.
For sports/performance cars without the huge price tags, there are the Nissan Skyline GT-R V-Spec, Subaru WRX STi, Mitsubishi Lancer Evolution, Seat Leon Cupra R (Spanish!)... all of which are considered sports cars, at least in Europe and Asia. Heck, overseas, they got some non-Italian sports cars you never heard of!

i thought we talking not just sport car but ultra luxury sport car which is only few been made and out perform the other regular sport car.
My answer yes italy is the one so i would rather rephrase the question " why are so many the best sport car built in italy? "

Well, It is just partially random that Italy has so many great sport car companies. Its not Italy only, Germany has Porsche, and those sport Mercedes, and Japan (has NSX), and other countries also have a few great sports cars. But there are a two sports car company from Italy that made Italy famous for sports cars, Lambourghini and Ferrari. When people hear the name of Italy and cars, they automatically get the image of sports car because of how famous Lambourghini and Ferraris are. Someone in Spain can try to start a sports car company but spain isn't famous for sports cars so success would be harder to gain.