Over C#:

* Garbage collectors often scare game developers since they can lead to hard-to-fix latency spikes.

* Rust has some cool libraries (specs, rayon, etc.) that let you safely parallelize computation.

Over C++:

* It's a memory-safe language, which instantly avoids tons of bugs.

* Library interfaces are usually higher-level in Rust than in C++, for various reasons (sum types being a big one).

* It's a much smaller language, so there aren't any dark corners that you'll randomly be forced to learn.

* It has an easy-to-use package manager, and I'm not sure where C++ is on that front.