Well, based on Chinese domestic service, I don't see 5 stars merit. I haven't had a really bad experience on them, but they aren't better than the other domestics (none of which deserves more than a 3 star average rating, IMO). As for basing it on international service, HU seems to get good reviews of the PEK-SEA route, especially in business, but I'm not sure I've heard people rave that it's up in the 5* range.
Personally, I have found the Skytrax ratings suspect for a long time. I don't even bother with the site anymore since I think a lot of it is based on airline pay-to-play. I mean, Hong Kong Airlines, seriously? That outfit has more problems behind the scenes than anybody wants to know--I wouldn't by a ticket on them if Skytrax ranked them 10 stars.