Pretty much all Digimon series are separate continuities, so you don't need to watch anime to get what's going in games and vice versa.
Cyber Sleuth is good old basic RPG. There are some few references for fans of series, but you are fine to start with Cyber Sleuth.
There is another new game, Digimon World Next Order for PS4, however that one is special pet raising RPG, which completely unique and is based on raising Digimon like Tamagotchi & virtual pets. Its quirky gameplay might not be for everyone's taste, but if you'd want to try something very different, it's a decent choice. And if Next Order is good, then if you can get it in some way, original PS1 Digimon World is also a fan favorite. There are more Digimon games, but they have their quirks which aren't that good for new comers. A lot of other RPGs can be grindy.
If you are interested in anime, but not interested in first season, the third anime series called Tamers is widely loved and one of the fan favorites. If the original series Adventure wasn't interesting enough, Tamers might be more interesting, as it has more mature themes.