They are entirely different.
Any resistor is a linear device, a transistor is nonlinear. A linear device has a linear relationship between voltage and current, simply put. Transistors show very much more complex behavior.
One is an interface, the other not. You cannot twiddle a transistor to change its characteristics.
A potentiometer is used to change a setting of a device, permanently at production, or during use. As long as it is not touched, the setting stays the same, being a passive device. Transistors can't be used to do that.
A transistor, being an active device, puts some of its characteristics, say the output resistance in relation to one of its inputs, say the collector current.
A transistor does exhibit resistance in the sense there is a voltage and a current, and when I measure those, it looks like a resistance. But when you change the CE-voltage, the current will not change in the same ratio. Say, you double CE-voltage, you will not get double the current, but rather nearly the same current mostly, making it a differential resistance. On any resistor, you would get a linear response, double voltage ==> double current.
This leads to the possibility of self-feedback on a transistor, making it possible to really regulate something, say in a constant current source. Twice the voltage, same current? Completely impossible with only passive devices, no resistor can do that.