Played Diamond 3 times technically. I first got it for Christmas in 2008 and played it the first time. Then while on vacation in Atlanta in 2010 I lost my copy of Diamond in the hotel. I only got 7 badges and never had a chance to beat Volkner or the E4. Then for Christmas 2011, I bought I new copy with my gift money. I messed around on the last guy's file, then transferred his Pokes to my White and HeartGold , and reset the game and started a new one. Though I wasn't satisfied with the new game I had so I restarted again. Now I'm currently playing through my third time around and I hope to actually beat the game this time. :D
Platinum I honestly didn't have until last Christmas (2012) when I bought I used copy with the money I got as a gift. I'm still kind of messing around with the last person's save so I still haven't played it myself in a way yet. So once I get a few more Pokemon (spefically Heatran) and then transfer their Pokemon to my other games, I'll restart the game and finally play Platinum personally for the first time.