Guessed by @Ultrashroomz
If the first game is arguably still the best because of its gyro controls and netcode, Splatoon 3 is the best because of everything else. It has a unique vibe that feels unlike either of the previous games, while also bringing back some of that wacky wild spirit of the original. It has the best soundtrack in the series (Anarchy Rainbow is an absolute joy), and obviously looks the best, even if it does show the Switch's age a little. The single-player campaign doesn't quite live up to the Octo Expansion, but it is still very good and we are likely getting another DLC campaign that is hopefully even better. Even Salmon Run is something I can have a bit of fun now, because of one minor change that made a world of difference (being able to throw the golden eggs around). I'm not a fan of them replacing Squid Beatz with Tableturf Battle, but the new mini-game isn't too bad either. As a whole package, it delivers for sure.
Obviously though, the multiplayer is the star of the show, and boy does it star. I mean, once you get past the 2 minute waits for each game, the communication errors, and the awful laggy netcode, all of which sucks. But apart from that, it's great. The new specials are super fun to use and mostly not too annoying to deal with, and the ranked modes are as balanced as ever. The map design seems to be getting some criticism from some corners, but personally I love nearly every stage in the game (only dislike the returning ones from Splatoon 2), I absolutely dig the more linear approach that brings back long range weapons into the meta. It just doesn't feel like Splatoon if you're not hopelessly trying to evade the E-Liter half the game.
Most crucially for me, however, was the timing of this game. Both of the previous games were great multiplayer experiences I had fun times with, but they always took a backseat to Smash as a competitive game. Since the release of Ultimate, though, my opinions on Smash have been dwindling, and having nearly dropped the game back in 2020, I've finally stopped playing it entirely earlier this year. It was fine having nothing competitive to play for a few months, but it meant that by the time Splatoon 3 came out, the door was cranked wide open for it to take over my life. I'm not sure I'll get to the point of taking it seriously, but it does feel nice to get into a competitive game that isn't riddled with broken DLC characters and comeback mechanics, for once. And the way this game came storming into my life really made me realize how much the Splatoon series means to me, and how awesome these games are - hence why I ultimately decided to list all three.