Flying the Grand Canyon in basic FSX/P3d isn't all that interesting. Doing it in Orbx North America open LC is only a little bit better.
As far as I know OZx Grand Canyon is the best available.
Well, it's been a while and I thought I'd check for any updates - Ta-Da! - OZX Grand Canyon and KGCN + HolgerMESH v2
The new version (2016) isn't all that different, but there are changes that make it worthwhile re-installing.
This is one of those sceneries that are a lot more fun to fly than just to look at the pictures.