One: there are no innocent bystander-type characters. This eliminates the careful-what-you-shoot factor, causing the gamers to lazily skim the environment careless of where he or she is aiming.
Two: the graphics are not up to par with other lightgun shooters. The developers plaster low-resolution sprite characters and textures over polygonal backgrounds, creating a mess of pixels that's hard to discern between a bad guy, a power-up, or useless debris.
Three: despite the many scenarios and branches within each, and without any variety in the action, the uniqueness of the situations blur together. Each situation just seems like the last. There are no positives to this game.
There are much better lightgun games out there, and you should leave Crypt Killer decaying on store shelves.