basically your perceived led brightness is proportional to display pause / (loop time+ display pause*2) (for 2 digits)

you have not set a OSC define so I'm assuming 4mhz clock and that your loop time is some mS lets say 5 so each digit led is on for 10uS and off for 4990 uS . its going to be dull.

if you make the delay pause too big the led will blink , it a compromise between brightness and blinking
try 500uS , its a trial and error thing I think and may take a few tries