Super Mario Odyssey is a Mario game in the style of Mario 64 and Mario Sunshine, meaning that it consists of a series of relatively open worlds with a variety of goals in each. While this isn’t my favorite type of Mario game, Odyssey may be the best expression of it so far.
The key gameplay innovation over its predecessors is that Mario Odyssey gives out Power Moons (the equivalent to Stars and Shines) quite generously. Instead of each world having a few large goals, they each contain dozens of small ones. While secrets would historically grant coins or extra lives, here they will almost always reveal Power Moons. This prevents the frustration of getting stuck on a particular objective (boss battles aside), and makes the game feel generally more rewarding.
The downside to having so many Power Moons is that Odyssey can feel like a collect-a-thon. In addition to the Power Moons, there are special coins to find in each world, and Mario’s usual golden coins are used as currency and a low-penalty stand-in for extra lives. The game provides you with lists and hints to find everything, but there is a whole lot to find and I’m not sure the fun needs to be stretched out that far. Still, the game comes to a perfectly acceptable conclusion even if you ignore this aspect.
Mario Odyssey introduces a new mechanic which essentially takes the place of power-ups: Mario now has a sentient cap he can throw at objects. Throw it at an enemy, and you can possess that enemy. Many enemies have special abilities, and the game makes excellent use of these to add new puzzles and interesting situations to the gameplay. Nintendo avoids grinding a fun mechanic into the ground, so there’s a ton of variety in what you can do. It’s an innovative and fun mechanic that works very well in the open-world style of Mario game.
The bottom line is, if you liked Mario 64 (and especially if you liked Sunshine), Mario Odyssey will fill you with joy. If you prefer the stage goal structure of Mario Galaxy, you’ll probably find a lot to like here as well, but this is not that game. Odyssey doesn’t focus on tightly designed gameplay (though it features plenty of it), rather favoring experimentation and exploration. Any 3D Mario fan will get something out of it, though exactly what you want from Mario will determine how much.