Ghost Recon, Ravenfield, Battlebit etc are shooters with simple graphics. Ghost Recon was from constraints of its time (2001 release) but Ravenfield and Battlebit could be way more photorealistic (like Squad) but chose not to. And I like that. In shooters you want good visuals if you can but having consistent performance is a bigger deal than some other games. I don't care about frame rate stutters in a turn based game like X-Com for example.

Speaking of turn based, one of the graphically simplest games I've playes recently is Armored Commander II. It is very very basic graphically (think dwarf fortress or intellivision) and I shit you not it is more immersive than it has any right to. The graphics and display info gives you juuuust enough info to set your imagination into overdrive to fill in the rest.

When your Sherman is almost out of ammo, bogged down in a muddy field and taking fire from enemy tanks in a nearby farm the actual graphics don't really matter so much