BJT Common Emiiter RF-Design Simulation
If you increase the value of RL, the bias point of the collector voltage drops. If it gets too low, the BJT goes into saturation operation rather than forward active. In saturation, the \$h_{fe}\$ parameter of the BJT drops dramatically so the gain of your circuit also drops.

If you're really going to use this in an RF context, you should include the load impedance in your model. It won't affect the bias because you've AC-coupled the output. But it will likely reduce the RF gain of your circuit substantially. 

If you don't consider the load impedance, you're likely to choose the wrong value of RL for optimizing the circuit's gain in the final application.