The answer depends on what you want to achieve. Even the best simulators are just that: simulators, so they can never fully replicate the experience of driving a race car but they are fantastic tools for certain things.
If you have a good simulator and you use it for specific things such as learning a circuit or practicing a new technique, they dramatically cut down the learning time when you are on track in your actual car. This makes real tracktime more productive as you are fine tuning your simulator experience rather than learning from new.
Appreciate the separation from real life and focus on specific goals and a simulator will be hugely rewarding.