Of the games I still have, Platinum has the highest play time at 322:40, and I think HeartGold has about half that. Unfortunately the two games I know may have had more time on them than my Platinum are gone, those being Sapphire (lost a couple years ago probably during a move, but I know it had over 300 hours on it), and Diamond (I was at a friend's house using his DS to transfer all my Pokemon to Platinum over a period of several visits, but one day his DS went missing along with my Diamond and has never been found). Emerald and FireRed get restarted all the time so there's no way they'd contend. Any games older than those have been gone for so long or restarted or ruined that I'd have no way of knowing their times.