Microsoft Flight Simulator. The last version I enjoyed was MSFS 2004: A Century of Flight. I had tons of add-ins, scenery enhancements, additional aircraft, customised AI air traffic, etc. The default install eventually expanded up to around 60 GB with all of the extras.
I ran it with Windows XP on an Intel Core2 Duo 2.0 GHz CPU PC with 4 GB RAM, an Nvidia 1GB graphics card & a 160 GB SATA HDD.
Performance was reasonable & I enjoyed creating flight plans & flying different aircraft on varying routes.
Fast forward two decades on, and if you want to use MSFS 2020 or 2024 (the 2 newest versions), you need a gaming rig PC with super-computing hardware specifications, & a high-speed fibre Internet connection, to be able to play it effectively.
This puts it out of the realm of the budget of most armchair aviators, and only dedicated aviation enthusiasts with VERY deep pockets can now play it to its full capabilities.
Maybe one day if I win the Lotto, I can then afford to play MSFS again...