Pretty much Real Flight. Currently RF 8 is the go to product. If your new computer has enough horsepower (and it needs a LOT), you can use VR goggles now in RF. See their forums for more discussions on compatibilities, optimal settings, etc. Almost any decent new computer can handle RF if used without VR.
RealFlight X was released a while ago, and was intended to be the future of the product line - much better graphics, and most of the 3rd party tools previously needed to create aircraft were no longer available for users, but were for RF X. But, RF X has it's own very high overhead for graphics that many users rebelled against, and it was missing many of the features that previous versions had had. Most that use it love it for the graphics. But....
A new set of 3rd party tools arrived that allowed users to create aircraft with the old software, so RF 8 was introduced to accommodate. The latest flavor of RF 8 is now branded with Horizon Hobby, and includes some of their planes along with SAFE flight controls. But, of course, all the old stuff is still there too.
With those developments, RF X has seen little love as far as updates, and speculation is rampant as to whether it will continue or not....
Most other name brands are gone.