I hate to say it, but around the time Shogun fans were starting to say he was the best ever, I couldn't figure out why. He defeated Rampage and Nog, but prior to that he lost to Babalu (the much smaller Gono was his biggest accomplishment up until that point).
His 5 biggest accomplishments after that were LHW Overeem, Arona, Machida, Liddell, and Randleman (some could argue Nakamura was better than Randleman or Liddell at this time?).
Machida has consistently had to fight tougher competition in the UFC (striking is his preferred style, and he's succeeded in the org. that supposedly favors wrestlers). I think his competition has been better, especially if you look at the names on Shogun's "best accomplishmenst" list and see how they were doing around the time Shogun fought them.
I think long-time mma fans would have to admit that they weren't surprised at all (I wasn't) at how Shogun's last fight went.