Just one game?
Meh, whatever!
I would try and re-make Metal Gear and Metal Gear 2:Solid Snake!
Give them both MGS3 graphics, get Harry Gregson-Williams to do the music, have the same voice talents as the MGS series (Except Big Boss of course, who shall be done by Donald Sutherland but more gruff and American lol), give them more of a challenging storyline, add the shot key in both of them (There wasn't one in either of the games xD), add flashbacks of MG in MG2 so new gamers would understand it more, I would get rid of the owl thing in one of them, keep the tap codes, but provide a guide in the instruction manual....
Basically, I would update them to newer times
EDIT: Oh and probably Castlevania: Symphony of the Night! Just make it uber lol