According to ESRB, this game contains: Animated Violence
Parents should take special note. There isn't any reason to be overly alarmed by the content in MGS, but I was rather surprised that the game was rated "E" for everyone. Though not visually graphic, there are a number of very dramatic moments (one enemy boss character sets himself ablaze and another mercenary reflects about how he killed his own brother in combat, and their mother committed suicide afterward). There is also no gratuitous profanity, but the script has many dark overtones about the effects of war, and there are some obviously mature themes.
Fans of the Metal Gear series are going to be in shock at how much the Game Boy Color version manages to capture the feel and the gameplay of the PlayStation one. In some ways, the portable version even surpasses its larger counterpart with tighter controls and extra modes like the two-player versus mode.
For any Game Boy owner who wants an instant classic, MGS is practically a sure bet.