My first memory of Metal Gear Solid was when I played it at a friend's house. I was probably 8 or 9 years old!
I recently replayed MGS1 on GOG and it was still fantastic, although significantly shorter when playing as an adult who knows it well.
At the time, I remember being blown away by the graphics which were significantly better than anything else I had seen. This, coupled with the games cinematic cutscenes and incredible characters was enough to set me up loving Metal Gear for life - I have played the entire series of games relating to Solid Snake and the games relating to Big Boss (except Peace Walker).
I will never forget when I first stumbled across the Cyborg Ninja in that corridor!
What are you defining memories of the Metal Gear series? How did you first discover the games and what has stuck in your memory?