Metroid on the NES. Fabulous game in its day.

I was around 8 years old or so, and I had Super mario Bros, of course. It broke before I could finish it (or I broke it, or something), and upon bringing it back they let me pick whatever game I wanted to replace it. I have no idea why I picked metroid, but I was so glad I did.

Shortly after defeating Mother Brain (a most joyous moment) for the first time, I discovered she/it was a character on "Captain N: The Game Master"

The second one I ever finished may have been Castlevania 2: Simon's Quest.....but I'm not sure