Its true gun games teach you how to shoot with precision/accuracy and to handle guns with proper care and discipline. As a hobby, its fun although expensive to pursue.
However, as a training ground for self defense situations, to me it doesnt seem to be completely practical or relevant. I think it will never totally replicate real world shooting situations where the targets shoot back and a host of dynamic circumstances are present. IMHO a more relevant, practical training would be the one which simulate actual shooting scenarios like the ones used by police and feds in the us where real service guns firing simunitions (paintball-like bullets) are utilized.