X-Com was amazing, and Xcom2 also pretty good. I just checked, and there is an amazing mod and very active community around LwotC (Long war of the Chosen), with tons of fixed bugs and improvements, a decade or so after the game was released. [0]
I am surprised Firaxis didn't work on an X-Com 3. I would guess the fan base is still huge.
I'm getting old and I don't play videogames anymore, but if I have a month of free time imprisoned in a cell with nothing else to do, I'd give xcom2 with LwotC a go. (and Master of Magic, and Master of Orion 2, etc).
[0]: https://www.ufopaedia.org/index.php/Long_War_of_the_Chosen
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