Oooo, that's a tough one since I doubt anyone has used a new version of every manufacturers cards (let alone one in each segment low-medium-high) so any answer you get would be based on a number of peoples opinions that someone has put together.
There shouldn't be any major difference though, except some might get better RAM to put onto the card and sometimes one might stray from the reference board design. Though all those things probably won't make more than a 5% difference but good RAM on the cards normally makes them better overclockers.
I haven't been keeping all that up to date about how each manufacturer has been doing but some do have a reputation, like Gainward likes releasing Golden Samples that are clocked higher than reference speeds (at a price), XFX also I think. Gigabyte loves having a premium price on their goods, Asus likes to try and appeal to overclockers, as does MSI. GeCube likes releasing rare things trying to grab niche segments (like their X1950XT on AGP for example, I think Sapphire does too).
Rating from best to worst is hard as everyone has bad times, so whoever is the best today has almost no chance of being the best tomorrow in such a competitive market and even then best at what, Price, performance, bundle, support, reliability? Noone will be best at all those at the same time.
Sorry not very helpful I guess.