Impossible to know. It is only a recent thing that we have ways to measure how many hours we have a game open (Steam measures this, not actual activity).
I played Diablo II multiple times a week for 8 years.
I played Quake 3 Arena weekly for over 10 years.
I've been playing Major League Manager (Baseball simulation game for DOS) since 1992-93. Its almost mind boggling. I currently play maybe 10 hours a month, been on a monthly schedule since around 2008. Before that, I can't say. I can remember playing it every day, and also can remember not playing it during the off-season. In the 90s, I played it usually during the baseball season, sometimes even following along the then current MLB schedules.