I was very good at 1.6 (barely lost 2 or 3 ESL online qualis, basically the last step before the LAN), near-pro at one time in CSGO, I'm still okay at it but have nowhere near the time required to be proper good at the game again.
We are.
Are you talking Marathon 1, 2 or Infinity? Or perhaps the predecessor, Pathways into Darkness. Or the slightly better known successor that is Halo lol
Such an enigma of a game - you can go through all Marathons just shooting and not giving a single crap, but the lore is 9 seas deep and goes on forever! If anyone CBA playing a mammoth of a lore game - Mandalore Gaming on youtube goes down the Bungie rabbit hole chronologically, great watch if you can spare the 3 hours.
Also wouldn't the OGs be System Shock (both 1 and 2)? Related - the System Shock remake's been out for a while but I've not played it...