How many worldwide average system processes and minimum process runs in Mac OS X? As I can check system processes in activity monitor, it is around 76 process running in my mac. 
As I assume if number of running system processes increases then it impacts on Mac speed.
If number of running system processes is high then Mac speed will poor , if it is nearest to average running process then Mac speed can be fair , if it minimum then speed will be excellent
Can anyone recommend or help me to identify that least number of system process and average system process runs in Mac.
Your assumption about inferring total system performance from the number of running processes is incorrect. There is no such direct correlation.

The underlying operating system easily scales to thousands of (idle) processes without any noticeable effect on system performance on a modern Mac. Therefore it makes no sense to spend effort on reducing the number of processes as such.