The short answer: there isn't a best brand.
Long answer: there isn't a best brand, because it's all opinion.
I know club riders who still swear by the skinny steel tubed bikes they road in the 80s from companies such as Ribble, Bianchi and Peugeot.
At the other end of the scale, I also know new, younger guys who swear by the latest mass produced carbon frames from main stream brands such as Trek, Specialized, Giant, Scott, Felt and Cannondale.
Then there's the leftfield guys who produce uber sexy titanium stuff such as Burls, Litespeed and Van Nicholas.
Then there's the custom frame builders who will make you something out of steel (in the UK anyways) such as Burls, Chas Roberts and Dave Yates.
It totally depends what you want. Just picking a mainstream brand like Cannondale and saying, "they're the best" is just wrong.
Personally, I have a Burls titanium frame. It's as light as some carbon frames, rides like steel and is stunning to look at. At the same time I'd love a Trek Madone or a Cervelo.
So, in my opinion, Burls, Trek and Cervelo!