In the virtual world I guess it is, it has along way to go to be the strongest in the real world.
Bitcoin is not even the strongest on the internet, just look at the amount of money paypal moves and that is just paypal, how much money is just move in a bunch of screens and with the clicks of a mouse, you can move trillions of dollars that way.
Correct and it is not just Paypal. There is Skrill, Neteller and Visa powered credit cards which is the most used when it comes to onlinr shopping.
Still it is USD which is the powerful and most used because of its popularity.
Bitcoin usage and transaction is just a small part of all that transaction that is happening in the world of internet.
Bitcoin is still just a small part in the overall transaction internet but if you will look bitcoin in the future for example, 20 years from now then you can easily imagine that bitcoin can easily replace those companies that you said and bitcoin can be the most used online payment system in the internet and become one of the strongest currency.