I can agree, some would put him in the top 5 of best field tacticians in human history. For example:
http://listverse.com/2011/01/06/top-10-military-field-tacticians/Here's a list of military generals, but Jackson is one of the reasons Lee is no. 11 in my honest opinion:
http://www.thetoptens.com/top-military-generals/http://topyaps.com/7-greatest-strategists-military-historyI find this surprising as he didn't even survive to make it at Gettysburg. If he did, I think he would've been given a more suitable force to handle, and would've easily have made it out as the best general in American History no question about it. In fact, most would say Gettysburg would have been won, giving the ANV a path to Washington to crush Northern opinion to sue for peace.
However, I believe the developers did not want the tip of balance to be in the CSA's favor too much, since the game's engines has its limits.