It's one thing to create a massive open world, but quite another to fill it with content and characters that players will actually find engaging. One way that developers attempt to achieve this is through the implementation of side quests and other non-story-related content, with the hope being that these additional activities will not only make these worlds feel more immersive, but also give players a reason to fully explore them.
Unfortunately, having put so much time into its creation, it's not uncommon for developers to try and shove all of this side content straight down the player's throat, which can often make it feel as though players are being punished if they choose to skip out on certain side activities in favor of focusing on the main story. Thankfully, these fantastic open-world games do no such thing, ensuring that optional side activities never once feel compulsory.
Shenmue
Not only is Shenmue one of the forefathers of the open-world genre, but it's also one of the best examples of side content done right. As they explore the streets of 1980s Yokosuka, Shenmue players will naturally stumble across a variety of pre-scripted events. Some of these interactions will lead to Ryo learning a new move, but most instead focus on further fleshing out his relationships with some of the game's many NPCs.
Though the additional lore is certainly a nice bonus, missing out on it doesn't really have any impact on the outcome of the story, so those looking to speed through the game won't ever feel as though they're being punished for failing to explore. If anything, the random nature of some of these events only encourages additional playthroughs, rather than making players feel bad about having missed out on them the first time around.
Judgment
Like the Yakuza series from which they spun off of, the Judgment games boast an awful lot of side content for players to enjoy. Given how seamlessly it can blend into the overall gameplay experience, it's clear that a lot of time and thought went into coming up with all of Judgment's side cases and other non-story-related content, yet it never once feels as though players are obligated to interact with it if they don't want to.
A big part of this likely comes down to series creator Toshihiro Nagoshi, who cut his teeth working beneath Yu Suzuki in Sega's famed AM2 division. Though all three of them are set in Japan (at least to begin with, anyway), Yakuza and Judgment are very different from Suzuki's Shenmue franchise for the most part, but there are definitely some similarities when it comes to the way that they integrate side content without ever forcing it onto players.
Horizon Zero Dawn
There's a real lack of innovation in modern open-word video games, with most conforming to the same tired concepts and ideas that have been around since the genre was first finding its feet in the late nineties and early two-thousands. These include having players find collectibles, mark off map locations by scaling towers or tall buildings, and claim territories by clearing out enemy camps, and can be found in just about every modern AAA open-world video game in one form or another.
This is once again the case with Horizon Zero Dawn and its 2022 sequel, Horizon Forbidden West, though the Horizon games do at least attempt to put their own spin on things, with things like Cauldrons, Tallnecks, and Vista Points. Better still, these side activities are never forced down players' throats as they are in some other open-world games. In fact, players don't even need to complete all of the games' side activities to unlock their platinum trophies, making Horizon one of the most generous and considerate open-world franchises in this regard.
Assassin's Creed
A lot of people like to blame Ubisoft for the current state of the open-world genre, with the publisher's formulaic cookie-cutter approach to game design having rubbed off on a number of other developers over the past few decades. This flawed idea that bigger is always better has had a hugely detrimental impact on modern open-world video games, with many considering Far Cry and Assassin's Creed to be among the worst offenders in this regard.
In their defense, though, neither series ever really forces players to interact with side content if they don't want to. This is especially true of the Assassin's Creed games, with players free to pick and choose which side activities they do and don't interact with. Choosing to skip side content entirely rarely has an impact on the overall gameplay experience either, ensuring that players never feel too bad about focusing only on the main story.
L.A. Noire
While Rockstar's GTA series has never placed too much of an emphasis on side content, the ability to unlock new vehicles and weapons or take part in unique missions involving main story characters can make some of the series' side content feel a bit like essential reading. The same is not the case with the studio's 2011 game L.A. Noire, however, with players free to completely ignore all but the main story without ever being made to feel as though they're missing out.
To be clear, some of the Street Crime side missions in L.A. Noire are a lot of fun to complete, while others are incredibly interesting and do a great job of further fleshing out the game's world. It never once feels as though the developers are trying to force players into interacting with the side content though, and the lack of any real rewards for completing it ensures that players are never really missing out on too much besides experience and the odd piece of lore.