Any sim is better than no sim, IMHO but the key is managing expectations and knowing what its capabilities and limitations are.
For instance, any at-home setup of MSFS can be used to learn what the flight instruments are supposed to look like during various phases of flight. Depending on the fidelity of the graphics in the sim, it can also be useful to compare these instrument indications with outside visual references.
Most at-home PC based sims are also good teaching/learning tools for the basics of VOR navigation. Even if you can't log the time (which you can't on most consumer PC based sims) it's still time well spent... makes your in-flight experience more meaningful.
Most sims are NOT useful, however, for learning how to land a real airplane because you do not get any control feedback. They are GREAT for instrument training though.
[shameless on-topic plug alert] My husband and I are both CFIs and last year we purchased an Elite PI-135 BATD, which is essentially a souped-up version of your at-home MSFS desktop setup. Ours has a complete radio stack with buttons and knobs (more realistic than pushing F4 or whatever to execute a command). It has a fully featured Garmin 430W simulator and input device, so it's great for initial avionics training.
We have our sim installed in a custom-designed desktop that we can setup inside our Honda Odyssey minivan, so we can bring it to the customer. This afternoon, for example, I have a lesson scheduled with a primary student, but the weather's awful here in DC. Since we can't fly, we'll use the sim to log an hour toward his required 3 hours of simulated instrument time. The PI-135 BATD can be used to log up to 2.5 hours toward a Private or 10 hours toward an Instrument rating.