Ninja Gaiden (for the Nintendo, not the arcade) was the first in a series of the best 2d side-scrollers ever. This game easily stands tall next to Metroid and Super Mario Bros., while maintaining its uniqueness.
It was one of the first console games to have cutscenes and a mature story. Best of all, though, players felt like they were playing as a ninja! Ryu Hayabusa was able to grab onto walls!
I played this game so much that I got good enough to play all the way through with one life without ever getting hit. And, when I had done that, I reset the game and started all over again. It was that fun.
Game Title: Ninja Gaiden
Release Date: 01st Dec 1988