Does instant coffee give a lesser buzz/high than conventional filter/french press coffee? I have felt that percolated/french pressed coffee keeps me awake more than instant coffee brew. 

EDIT: Since it was (validly) pointed out it will depend on the amount, so the amount, that I am comparing is basically what is mentioned on the packet of instant or ground coffee (whichever is the case). 
As in if my instant coffee sachet says it makes 2 cups of coffee, I use half of it. And if the ground coffee says to use the filtrate of 2 tablespoons for each cup, I do the same.
Caffeine content varies greatly by preparation and brew method.  Instant coffee is generally designed to produce something close to a cup of drip coffee.  "Cups" is unfortunately not well defined and may vary based on it's usage.  Beyond that, percolated and french press coffee is generally prepared stronger (more concentrated) that regular drip coffee (and probably much stronger than the watered down concentration instant is designed for).  It's also very likely that some amount of caffeine is lost during the freeze dry process since it is so water soluble.  

TL;DR Yes.  Real brewed coffee will generally have a higher caffeine concentration than coffee that has been brewed, dehydrated, then re-hydrated.