China alone has over 300, including modern versions known as the SU-30MKK. India has 40 SU-30s and licenses to make 140 more. There are 449 SU-27s in service in Russia. Lots of other folks, like Vietnam and Venezuala have them or have them on order.

The SU-27 has seen very limited combat by the Eritrean AF.

The list of countries procuring the Flanker is a long one, many of whom could be potential adversaries, although the liklihood of fighting any of them is arguable. Some of them, such as India, field very well trained pilots indeed. Others probably are very clueless on modern tactics and wouldn't use the aircraft near its capabilities at all.

I do agree, that the timeline for designing and procuring takes far too long. The whole acquisition system, starting with the POM, needs to be completely rethought.