I cried manly tears while lifting wieghts the day Duke Nukem Forever got a release date!
....
Ok more seriously, I have it happen a lot, at least getting emotional while not necessarily crying my eyes out. I've been told its for all sorts of reasons in the past but personally I think its due to me being (or at least I liked the way one of my friends put it best) "emotionally sensitive with an active imagination". It helps me get invested in a game, its world and its characters to the point even things that werent necessarily intended to be emotional strike a chord with me.
Prime example, it was an odd one that I didnt expect, was playing far cry 2, and had one guy (Paul Ferenc, god rest his computerised soul, myself playing as Hakim) who had been my best buddy since my first mission, always going to him to help me and giving him a hand with his problems too, and he had saved me a few times aswell.
I know it might seem strange but I had got pretty attatched to that guy, props to the developer for making my link with a character so well, particularily one that, in essence, is interchangable with any of the other characters in that game. He just happened to be the one who was chosen randomly to phone me up when I did my first mission.
Then I did this one mission and at the time I had no idea that your buddies had a sort of "3 strikes and out" system (on the xbox one I played anyway, dont know if thats universal), I had only let him down twice before so when I saw the blue flare after I had finished off the remaining guys I sprinted over too him, thinking "I've got the spare injection, he'll be fine in no time"... then when he took the fist and didnt get better I was confused but thought "I've got 3 more, maybe he just needs some more this time", then a third went in and he wasnt getting any better and I thought "hey come on now this isnt funny, get up, get up!", then my character lay him back on the grass as he let out a last sigh of life and closed his eyes.
What made it even more poignant were the words that came in the "achievment unlocked" message at the bottom of the screen, "goodnight, sweet prince"... I must have sat there for half an hour in shock with tears in my eyes...