That's funny. I think Exxon/Mobil has 8% of the gas market in the US. No competition there.
When I was growing up, way back in the last century, in addition to the biggies, there were a host of independents. Along with your purchase of gas, were "gifts" like dishes, glassware, flatware, and toys. Sometimes they had "gas wars" and one could purchase gas at ridiculously low prices, even for the times.
When one pulled into a gas station, a young man ran from his shelter, to your car. He not only pumped your gas, but washed your windshields (front, back, and even side windows on occasion), and asked to check your water and oil. If a tire was low, he put air in it (for free!).
That my friend, was competition and service.