I only plat games that I enjoy. That said I am sitting at 3 currently:
Demon Souls (Have beaten it once after the plat for good measure)
Final Fantasy XIII- I enjoyed the game from top to bottom, but getting the platinum was by far the best part.
DragonAge- The platinum required 3 full playthroughs on the three different classes. I was going to do this anyway.
I want the Atelier Rorona Platinum but it will be a good while until that happens.