Can't disagree with any points being made in favor of Splatoon 1 here. It had the best netcode by far, and the Gamepad's gyro controls were far more precise than those of the Switch Pro controller. Matchmaking was fast and the ranking system was fair and objective. Later games had more maps, more weapons, more versus music, improved battle modes and arguably better balance, but even in spite of all that, it's hard to argue that Splatoon 1 didn't have the best multiplayer experience. The netcode alone basically makes up for everything else, oh and also it was free. And as a bonus it also has the best final boss in the series, although the campaign overall is not as good as the latest ones.
Splatoon 2 has the best single-player campaign by some distance, albeit behind a paywall. It also has a functional version of Squid Beatz, unlike either of the other games. It had good music, good characters, introduced Salmon Run which was... fine? But online multiplayer was ruined by bad map design that put too much emphasis on short-range weapons and flanking, honestly it was a pain.
Splatoon 3 has easily the best map design in the series, a very good single-player campaign, dramatically improved Salmon Run with only one tiny change (being able to throw the eggs), great balancing that's bound to get better, and has a great vibe like the first game did, but very much different in style from its predecessors. For me it's the best game in the series, but it's ruined by bad netcode and the ridiculously long waiting times to get in a game. Hopefully the latter can be fixed, but I feel like the tick rate problem isn't going away until the Switch does. And hopefully the next console has gyro controls as good as the Gamepad did.