I love the GTO. It looks beautiful, it performed (for its day) and it was EXCEPTIONALLY RARE and expensive.
If I remember correctly the GTO was released to customers a few years before the 959 so the GTO wasn't built to compete with the Porsche. The 959 raced Rally, I don't think Ferrari ever raced Rally. I might be wrong regarding that though. The F40 was more a contemporary and competitor of the 959 than the GTO was.
The F40 was spectacular, a better performing car than the GTO but something about the looks of the GTO just does it for me.
When I was a kid there was a Ferrari dealer in Cohasset, Massachusetts right on Rte. 3A that had a GTO in the showroom. I used to go and drool over it once a month. There was a Maserati dealership across the street too, that was a cool street for a kid.
I believe right after Enzo died GTO's were trading for $1,000,000. I think they're selling for around $500,000 now, but they come on the market so rarely who knows.
This is the basis for the road going 959 that was sold to the public.