My stepbrother was laying this one on me.
The concept here is that if you're all serious about your gaming and shit like he is, than you have won the game without any aid from friends or family. The stipulation is that you and only you held the controller throughout the duration of the memory/game.
When I got thinking about it like that, I was shocked how many games I haven't won by myself in comparison to how many I have played. There is a lot of games I played and enjoyed when I was a wee boy and in reality don't have any claim to have said that I have won myself because I was playing them with someone else or had help from someone else with some part along the way.
So, try this. List every game you have ever won on your own. That means you know for certain that no one aided you (by way of controlling the character(s), someone telling you where to go or what to do is fine). Cheat codes, save state, etc. count just fine, so long as you personally did all the finger work. You cannot count 2D fighters unless you won them on the hardest difficulty setting with 2 or more characters. Racing games and first person shooters also have to have been won on the hardest difficulty to be counted.
When I look at it like that my list becomes surprisingly short:
Crisis Core
Final Fantasy VII
Mario 64
Mario Kart 64
GoldenEye 007
The Legend of Zelda: Ocarina of Time
Super Street Fighter II HD Remix
Street Fighter IV
Super Smash Bros. Melee
Ninja Gaiden Black
Ninja Gaiden II (XBox 360)
Kung Fu
That's all I can think of I'll add more if they come to me.
If you read this and are thinking to yourself There is no way in hell I could list every game I have ever won then you are like my stepbrother and you play video games A LOT.