1) Street Fighter 2- The grand daddy of all fighting games. It did for games what Star wars did for movies. Memorable characters and special effects.
2) Metal gear solid- Created a whole new genre of game the "stealth 'em up". It stands alone with a great storyline and blend of stealth and action. Even Hideo Kojima has failed to give us a sequel that's as much fun to play.
3) Mortal Kombat- This deserves a mention simply because it brought gore to the mainstream with the "Fatality". There's nothing like being able to rip your opponents arm off n hit him with the soggy end, it's a satifying conclusion.
4) Grand Theft Auto- From it's 2D heyday to present 3D this is possibly the first "sand box" title. On the PS2/Xbox is when it hit it's prime with "San Andreas". With gangs and customisable cars it's a shame GTA IV didn't follow suit.
5) Final Fantasy 7- Goes down as the gem in the RPG crown. Square has struggled ever since to bring to life characters in such a way along with such a compelling story.
Each of my choices are based upon the fact that all five have spawned clones. Not only that but certain eliments are now seen as a requirement in games. No fighting game is complete without special moves. Most importantly the easily recognisable character that the player creates a kin-ship with. All choices are in my own humble opinion based upon my time as a gamer.