I'm afraid you'll have to define your terms. Best at what?

And you should also be aware that most of the "brands" don't make their own frames. Giant do, from scratch, spinning their own carbon fibre. They supply many other bicycle brands with frames, but those frames will differ markedly in specification, price, geometry and so on. And then there are many other generic manufacturers, especially in the Far East, who supply frames to bike makers all over the world. And there are a number of highly sophisticated, low volume, custom builders. Here is an informative article on the subject.

As far as the bikes used by pro teams in the Tour de France is concerned, here's a review of ten of them. Once you've read those accounts, you'll realise that the question "which is the best" has no sensible answer.