Me (And I am only going to include the completed games too!):
- StarCraft. - Including it's Nintendo 64 release and the Insurrection and Retribution expansion packs.
- Diablo. + All console and PC releases. (PS1, Switch, Xbox 360/One, Playstation 3/4)
- Dragon Age.
- Mass Effect.
- Halo. Including the Windows Phone releases of Spartan Strike and Spartan Assault. All Windows and Console releases.
- Heroes of Might and Magic.
- The Settlers.
- Civilization.
- Sim City.
- Unreal+Unreal Tournament.
- Crysis + Every Console release.
- Kings Quest.
- Dune.
- Mech Warrior.
- Gauntlet.
- Descent.
- System Shock.
- Portal.
- Half Life.
- Grand Theft Auto.
- Elder Scrolls.
- Fallout.
- Baldurs Gate. + Including OG Xbox releases.

Every 3D Zelda game
every 3D Mario Game (almost every Mario game tbf, bas NSMB U)
Smash Bros
Luigi's Mansion

Once I get the latest Prof Layton I'll cover that too

I've played every Luigi's Mansion game.
Every Mario platformer (I only played the 3DS version of the first Mario Maker).
Every 3D Zelda game, from the 2D games I'm only missing Four Swords.
Every Doom game.
Every Donkey Kong Country game.
Both Ori games.
I think that's it.

The only series where I've played every game are:
Luigi's Mansion
Super Smash Bros
Professor Layton (including the Ace Attorney crossover and Layton's Mystery Journey)
There are plenty of series where I'm only one of two off the full run like Zelda, mainline Mario, mainline Pokemon, Ace Attorney, Mariokart, etc.

Many but only listing series with 10+ entries.

- every main Call of Duty game (excluding the spin off Finest Hour, I did play Big Red One though)
- every Assassin's Creed game (currently playing Valhalla)
- every Halo game (except the PC/mobile exclusive spin off Spartan Strike)

Legend of Zelda
Chrono Trigger/Cross/Radical Dreamers
Dragon Age
Infamous
Xenoblade Chronicles
Devil May Cry
Bayonetta

Are the franchises that jump out at me.