UK Top Gear is unbeatable, it is the most popular TV show on Earth and has one of the largest budgets.
The others are copies.
It would be UK, then AUS, then US.
The US version is the lowest, because as stated in an earlier post. It is a contest between Challengers, Mustangs and Corvettes etc every week. And in one of the challenges I watched the "loser" car was generally a superior vehicle to the cars they had bought.
The "Alaska truck challenge", the loser car was a Toyota Hilux.... the best Pickup truck on planet earth... yet it was the "loser" car because it was Japanese...