For historical perspective developed in parallel with Half-Life 2, Medal of Honor: Allied Assault is worth a look. With Call of Duty being the revenue juggernaut it is now, I think we sometimes forget how it started. Allied Assault is a landmark game that’s an ancestor in CoD’s lineage.
On the other end of the timeline, the founders of the studio that developed the original Call of Duty went on to make Titanfall. Titanfall 2 has an excellent single-player campaign that holds up very well.
I still distinctly remember the first time I used a bedroll in Divinity: Original Sin 2 and knew immediately it’d be impossible for me to ever go back to the first one.
I enjoyed the original D:OS a lot more later once I had more chances for XP. Both D:OS games are brutal about punishing you for trying encounters while underleveled, to the point where I didn’t feel like I had much flexibility. That’s tough when freedom to roam and not worry about skipping things–or saving them for replays–is one of the things I most like about Western RPGs. I wasn’t a fan of spending a ton of time in town early on, too, for that reason. Was itching to get to the combat again and I just kept getting stomped. So yeah, okay, I’ll go chat everyone up for every last bit of experience.