It really depends on what you want.
FG is an OpenSource product, which means it doesn't make profits by being sold, which in turn means the ability to sell or market it doesn't influence development.
That means that it comes with some features out of the box which might be somewhat hard to get otherwise (out of the box a detailed light scattering model in the atmosphere, the ability to let it drive 10 screens of a cockpit from multiple graphics cards, the ability to connect to a tablet to a running session via http and use that as an instructor station to monitor performance and cause failures,...) but also that (dependent on what you want) you may need some time to learn configuration etc. and you may need to write some xml to get your control HW supported properly.
Quality of airplanes varies correspondingly compared to a product that needs to be marketed - some are just rough and unfinished by people who enjoy tinkering a bit, others at the high end couldn't be marketed because they require you to train like for the real thing before you can get anything done and only few people put up with that.
Since it's free, you can just download the package and make up your mind whether that's what you want or not.
(And please don't call it a game - the JSBSim code driving the flight dynamics is a research and industry tool, benchmark-tested against NASA simulation codes and FG is (among other things) developed for research and industry applications,...)