Basically asking which game would you keep playing regardless on how many years passes, you always play that game every year (doesn’t matter how much time).
In my case that game would be Risk of Rain 2. Each year me and friends play some runs and have a lot of fun since it was on early access (we always play a few months every year)
Which game will you keep playing?
Any of the Monster Hunters. Specifically Monster Hunter 3 Ultimate as it was my first game in the franchise but I regularly return to all the titles since that and at some point I plan to play the older ones too if I find some time.