I have long wonderd if the Jas 39 is better then all American planes up to F-18 Super Hornet. By that i mean planes like F-16, F-14, F-15, And Of Course F-18 Super Hornet.?

It depends on the role. In a dogfight in a equal pilot situation it would have the advantage of the 15 and 14 and porbally the 18 but might be troubled by the agile little viper. In a BVR arena though it really doesnt have the advtanage against any of those fighters, especially upgraded AESA versions of the F-15.