there is no longer any rhtme or reason for most things... just look at the title of the next Red Dead game lol.
Pretty sure that's just brand recognition, though. Most people know what a "Red Dead Redemption" game is. If it were Red Dead R... something else, many people won't be sure. Sticking a 2 on the end is the easiest and simplest. Red Dead is popular, but it's no Grand Theft Auto. There's definitely a rhyme and a reason for its naming.