Some people may truly know which company made the ad, but I'd bet few could guess if the ad was made by Coke or Pepsi without watching it again. Many companies, in addition to Coke and Pepsi, are similar in that their ads do more to prevent customers from buying other brands than they help customers choose between them. One example is Mastercard and Visa. The main message I get out of their ads and my own experience is that they are virtually the same, but no one accepts American Express. Nevertheless, my choice for long distance will be one of the three, not some other company.
Some major companies do tend to stand out through their advertising.
The most prominent example is Nike. Everyone knows the difference between Nike and Reebok. The difference is their advertising. Nike's advertising is one of the main ingredients of its success. Reebok was not a viable option.