When i had 0 health and managed to get through 2 characters in a row and win, Tiger Uppercutting my way to victory in front of everyone in the arcade i was in playing Capcom vs SNK 2. Definitely the most powerful moment ever expressed from a video game.

Sometimes, the most memorable moment in a video game come not from pretty CG or story seen sitting at home, but experiencing it outside the game from the OOOOOH's / cheers from the huge crowd watching and the competitive atmosphere in an arcade. Then shaking the opponent's hand in real life for a good game.