I typically never lay claim to just one game as being best, regardless of genre.
Over the years though I have grown attached to some that I either played to death, made extensive video walkthroughs of, or both.
I'll start with a few of the more obscure titles that are often overlooked.
Spec Ops The Line
This is a shooter with a very unique and well written story where the protagonist is stuck in a state of cognitive dissonance. Not only is the story and voicing very well done, as you can feel both building to the state of mental breakdown, it also has very deeply touching emotional scenes. Beyond that the gameplay demands you work well with your squad, and choose weapons wisely, as they carry over into the next level. It's a game that is very challenging and demands full attention on the hardest difficulty mode, yet if you position yourself well, and work well with your teammates to take out normal enemies and suppress heavies, they are MUCH less likely to require reviving.
Kane & Lynch 2 Dog Days
Like Spec Ops The Line, this is another shooter with very visceral combat, and the need for teamwork, but in this case, you have just one to work with. This is another game where how you position yourself, the pace you go, and knowing when to move forward are key to success. This game is definitely more over the top than Spec Ops The Line, but it has some epic battles where you fight a good variety of enemies using a range of weapons.
Stranglehold
Produced by John Woo, this is a sequel to his movie Hard Boiled. It's protagonist is "Tequila" whom has the likeness and voice of Chow Yun-fat, and uses a bullet time mechanic called Tequila Time. This is a very arcade game where you can dive, slide down stair railings, belly slide on tables or rolling carts, or swing from chandeliers to shoot enemies. There are also many interactive objects you can shoot to take out enemies, like signs above that fall on them. Tequila also regularly faces more than one foe in a standoff, where they are standing pointing a pistol at each other. When the action begins you must shoot and dodge while standing to survive. Tequila also has a spin attack you can use where he spins 360 taking out multiple foes. In this game you are rated by a star system that rewards more points for spectacular kills.
Honorable Mentions
Terminator Resistance
Not necessarily a blockbuster title, but the best homage to the movie ever put to game.
Now for the ones that most know pretty well.
Black Mesa
A masterfully remastered version of original Half Life using the Source Engine. What's not to love?
Resident Evil 4 HD Project
The incredible RE 4, but with significantly improved textures throughout the game.
RealRTCW
The original RTCW with new renderer, HD textures, and adapted to 64 bit. This is THE best way to go back and play one of the best classic shooters of all time. It's such a popular mod you can get it on Steam.
The Entire Gears of War Series
I've played every one you can on PC, and had a blast with each one. I guess I could have put this in the bittersweet category since the epic original cannot be played on PC anymore due to the long since defunct Games for Windows Live service it was built around making it crash. I mean they couldn't even get the GoW Ultimate Edition PC version to work right. But despite that and my loathing for the way they designed The Great Escape mission of GoW 4 (which has still kept me from beating it on Inconceivable), I avoided putting it in the Bittersweet category due to having thoroughly enjoyed Gears 5, and am actually looking forward to what's next in GoW because of it.
Machine Games Wolfenstein Series
I've simply loved every one of them, including the spinoff Youngblood. A very good homage to the originals, with a new take in more modern times, and a well crafted story that's emotionally written and voiced, with some good humor thrown in. Where it really shines though is the incredible gameplay, great weapons, and stunning graphics.
Entire Halo Series, and especially Halo Infinite
I finally got around recently to playing all of the Halo games that can be played on PC, beat them on Legendary, and loved Infinite so much I made a complete video walkthrough of it on Legendary with no upgrades. All are great games, but Infinite makes me anxious for what's to come. The Grappleshot really changes things from combat, to pickups, to navigation. If you choose to completely upgrade it, you can do devastating shock punches with it that makes you look like a superhero.
And now some that are rather bittersweet.
Ghost Recon Wildlands
An excellent game, and IMO best GR ever made. Another game I loved so much I made a complete video walkthrough of on Extreme with no HUD or upgrades. The bittersweet thing is Ubi have gone crazy since and turned Ghost Recon into a Sci Fi fantasy tiered loot game ala The Division, except the location it's in is fictitious too.
Doom 2016 and especially Doom Eternal
These to me are easily the best Doom games ever made, especially Eternal, which has a hugely broader scope than any other Doom game made. The Meathook also makes it feel completely different and very fun, as well as a dream to navigate terrain with, and even bypass tough enemies if you choose. The bittersweet thing is their decision to instead of take a few years and make a decent length 3rd installment, making it an official and deserved trilogy, they chose to rush out two short DLCs. The Ancient Gods Part 1 and 2 are also not progressive in nature. Instead you're given all weapon mods and skill upgrades at the start, and the gameplay is mostly non stop waves of enemies.
And I'll finish on a positive note.
Biggest Surprise
Titanfall 2
I never thought Titanfall would get an SP campaign, let alone one so good and so long. Respawn are one of EA's best dev teams, and IMO they are damn lucky to even have them.