The amnesia element is only used primarily straight in the main character. Every where else it's played for laughs. Heck Ghost Trick should receive an award for being one of the few games to have a clever, and brilliant reason for the amnesia cliche.
After all it's not so much "amnesia" as it is mistaken identity. Sissel can't "remember" his past because he's trying to remember the past of someone who isn't him; kinda hard to do. XD
In the GI reviewer's defense, all I have to say in response to this "clever and brilliant reason" is: Final Fantasy VII.
though, actually being a CAT is way cooler than being a subpar soldier who wants to be the cool soldier.