Safety would be a toss up between them. They would all have roughly the same robust safety features. Here would be 2 differences:
Rollover risk: (I don't know the math on calculating rollover risk, but vehicle width and ground clearance are 2 very important factors).
-The Lexus GX is the lowest with 8" of ground clearance. However it is also the thinnest.
-The LC200 has 8.9" and the widest stance.
-The 4Runner Limited and Trail have a ground clearance of 9.6"
Side Impact based on vehicle width. (There is much more to side impact protection than just a vehicles size, however since all 3 vehicles have almost identical safety systems...)
-Lexus GX 74" wide
-4Runner 75.8" wide
-LC200 77.6" wide
So the LC200 would most likely have the advantage with Side Impact. The LexusGX may win with Rollover, but because it's the thinnest I don't really know. The LC200 seems like a good middle ground with Rollover risk because of it's wide stance. Unfortunately the NHTSA does not test the Lexus GX or the LC200. Here is the rating for the 2010 4Runner:
2010 Toyota 4Runner 4-DR. w/SAB | Safercar -- NHTSA
You can see it's great, except for rollover (as with all SUV's). I would imagine the LexusGX and LC200 would get 3.5 stars for rollover risk, only slightly better than the 4Runner. If you want 4 stars you'd have to get a Toyota Highlander, 5 stars a Toyota Camry. Or, as a realistic option there is the Lexus LX which has AHC that lowers and inch at high speeds and reduces center of gravity. It's conjecture but that might get 4 stars as well.
As a note, the LexusGX and Toyota 4Runner where redesigned in 2010. As you know the LC200's where introduced in 2008. So you could keep an eye out for a used LC back to 2008. The 2008-2009 LC200's that I've seen have been pristine. I've seen pricing around 55k.