A game I love is the “Resistance: Fall of Man” series from the PlayStation 3 era. These games are the PlayStation equivalent of “Gear of War.”
The games follow the tragic stories of the battles fought by remnants of humanity against an alien horde/virus that is infecting all life on Earth and driving humans to the brink of extinction.
The games take place in the 1950s during a timeline in which World War 2 never happened. Most of the battles are across America, England and France, with guns and vehicles representative of the time. There are vast hordes of alien monsters, ranging from message walker types to alien goliaths the size of towers with all sorts weapon thrown in the mix. The game play is very much fighting all sorts of enemies and has so much creativity and variety to how it plays out. It has a massive selection of guns and weapon.
The story is amazing, and captures the themes of World War 2 well, but takes them to a much darker level. The game really dives deep into many science fiction elements.