If half the people who posted here read the Books or something then you would learn that Mace Windu indeed was a badass... even Yoda couldnt hide his feelings from him. But that was through training, not through force potential.
I cant remember who said it but they are right, "survival of the fittest".
the only problem with that is that the force is like the air we breath. Some places there are higher concerntrations and it moves freely throughout the galaxy. Depending on where a Jedi was or when they were alive then that made them gain more ability to use the force.
Now everyone hates the Midichlorian counts in the new episodes but they are just being ignorant really... it explains why Jedi force powers can diminish and become stronger as, the force is described as i have above in the books. The more Midichlorians you have, the more of that Force you can gather to your will to a certain level and if there is not enough Force persay each midichlorian then the user would intern be weaker.
Palpatine and Vader killed all the Jedi and this somehow damaged the force. Every Jedi that dies takes a part of the force with them through their connection to it. Every Jedi and Sith War slowly killed the force making it weaker and weaker in places all over the galaxy.
Hmm maybe somemore after i realise from peoples posts what parts ive left out and made ambiguous...