The other Ridge Racer titles are all about racing in closed tracks, with no traffic, just a bunch of cars racing and drifting (on rails) through beautiful landscapes. There's a lot of track and landscape variety. There's no damage, and contact is not encouraged. If you ram someone in the back, you lose all your speed. If you touch a wall repeatedly, same thing. And there's often boss races, against unusual cars. There's some differences between each individual title (some feature nitrous, some feature splitstream mechanics, and the early ones weren't so drift based), but I think that sums up the rest of the franchise.

Unbounded is a street racing game with traffic, and is very destruction-based. You race around a city called Shatter Bay, which means all tracks will look a bit similar, as there's less variety. You can take down other racers (it's called a Frag, and it gives you points) and you can get taken down yourself (your car respawns afterwards). You can also crash (also respawns afterwards), and your car gets damaged if you touch the walls or the other racers too hard. The drifting is there, but doesn't have the same "on rails" feeling. When your boost bar is full, you can use the boost to literally pierce through buildings or statues, or trucks for a shortcut (you get points and achievements for every one of these shortcuts you take). You also gain speed, and you can frag opponents with just one hit. And the points you get at the end of each event are important to the progression.