Hi, this forum is meant for X-Plane default install. Surely, Laminar Research did not reduce the quality of the existing scenery.
Provided you are not using X-Plane Steam version, I would recommend to :
-Remove the third party sceneries you installed (the problem is very likely to be caused by them).
-Update X-Plane via the installer which can be found here :
http://www.x-plane.com/kb/digital-download-install/
-Check if the scenery is as good as expected when running X-Plane
If you want to try again the third party addons you purchased, make sure you follow carefully the installation instructions that are most likely included, or contact the developper of these addons.
If you are using the X-Plane Steam version, contact Steam for support.
You could possibly find some help on X-Plane.org forum also.
There's nothing much one can say without your ...X-Plane/log.txt file. If you decide to included it, make sure you launched the sim at Pearson/New York and closed it prior to uploading it here.
Regards,
Guillaume