Top speed is the Holy Grail among a lot of people. Top speed is limited by incline of the road, how much wind resistance you encounter, altitude, and the displacement of the engine. When the torque out of the engine equals the resistance of these four factors, your speed goes no faster, regardless of the number of teeth utilized in the rear sprocket.
Like a four-wheel vehicle, with a downhill, strong tail wind, or big engine, you can go faster in higher gears. In lower gears, the engine becomes the resistance. You have seen big trucks go down long inclines (well, maybe not in Florida). In Colorado, engine braking is mandatory to avoid runaway trucks. (Lets see.... a 9,000 gallon gasoline tanker with no engine brake nor friction brakes doing 120 mph equals.... a lot of excitement.)
There are all kinds of fun comments from some writers how fast their bicycle went, like one who claimed 65mph (while it was strapped to the back of his pickup truck on the interstate.)