The sad feeling when you end a good video game...

Sometimes when we can beat a game we have the that sad feeling of emptiness and the same time happiness... is like when you finished your favorite book ( I know is a totally different thing) but the feeling is similar.  

You dont really want to finish you game ( at least thats my perception) you wanna beat it off course you dont want to finish the entertainment. 

I think the first game that I beat was Mario Bros. was kinda cool and full of joy !! but then... that feeling , feel empty cause you just pass over the game! is nostalgic ! what was you first game that you beat?