What is the best preamplifier circuit for electret condenser microphone?
Add a resistor in series with the 100 uF capacitor across R3 as shown below: -



Without that resistor there is nothing that defines the AC gain of the amplifier and the effect of the 100 uF without the 1 kohm resistor will make the input impedance very low and significantly distort the signal from the microphone.

With the 1 kohm resistor I've added, the circuit AC gain will be around 22 and the input impedance will be around 10 kohm.