first, I DO believe the Greats are under Xiao Feng (no one in his/her right mind would believe Greats > Xiao Feng).
second, I DO believe Guo Jing > Greats
next, I DO believe Xiao Feng has more power than Guo Jing. But based on their fighting style, Guo Jing has an advantage which I will not overlook.
Guo Jing's style preserves energy, which allows him to perform better in the LONG term. Xiao Feng's long distance attack exhausts energy, which allows him to perform better in the SHORT term.
Now people claim GJ CANNOT perform long distance attacks a la Xiao Feng. I'm not saying GJ can, but it doesn't fit his model, so it doesn't make sense for him to do it EVEN IF HE CAN.
As seen in XF's fight with You Tanzhi+MRF, exhausting raw energy has a major disadvantage because he will run out of power sooner than GJ.
Let me make a silly analogy here. A fight is like a race. If the distance is 100 meters, then the fastest runner will win. However, if the distance is a long 10000 meters, then the one who preserves energy best will win. The fastest runner who exhausts energy at the start will not prevail (which is, if I am not wrong, a big no-no in running).
You could argue that GJ might not last long enough to see the effect come in. But he took on Golden Wheel Monk (who was already stronger than GJ) plus Nimoxing and Xiaoxiangzi (who together are in my opinion more difficult to handle than YTZ+MRF - now, do NOT misunderstand me again. I am not saying GWM is stronger than MRF or YTZ. I am saying that, Golden Wheel Monk ALONE is stronger than GJ, whereas MRF alone would be squashed by XF, and YTZ alone would be squashed by XF, but GWM is STRONGER than GJ, plus he had the help of two great men, so GJ's opponents are more difficult for HIM [GJ] to handle than XF's opponents were for XF to handle), and GJ was handling the situation better than XF with YTZ. Is XF > Golden Wheel Monk, Xiaoxiangzi, AND Nimoxing? Debatable.
I hope I have made my points clear! To recap:
-I DO believe Greats < Xiao Feng
-I DO believe Greats < Guo Jing
-I DO believe Guo Jing < Xiao Feng in power, but XF < GJ in fighting method, so GJ =~ Xiao Feng when all factors are considered