I already said, Rory fight was the only embarassing fight he had outside of 155. That fight marked a sharp decline for Penn, a big dropoff. Diaz fight he won the 1st rd, so don't know what you're talking about that he didn't have a single good moment in that fight.
Penn is not a GOAT, but he is the LW GOAT. Read this to give you an idea. Too many people just focus on W-L without looking at context. Barao was like 30-0 or something like that, but almost all his wins were vs guys no one had ever heard of, like 80-90% of his wins. I mention Barao because he's an example that people can't go strictly on W-L to judge a career
http://www.sherdog.com/news/articles/11/Sherdogs-Top-10-Lightweights-of-AllTime-118077