Battlefield V was one of the first games that got Nvidia RTX support with DXR Reflections but it was plagued by various problems as well as a big performance hit, by up to 20 to 30 percent. With the introduction of DLSS support in Battlefield V, that same performance hit was negated, although with a slight hit on image quality, as DLSS render the game at a lower resolution and uses RTX Tensor cores to upscale the image.
In any case, DLSS is a big addition to Battlefield V and will push the use of RTX effects in the game.
Unfortunately, there are certain limitations to enabling DLSS in Battlefield V as it can only be used with RTX enabled and at certain resolutions. Techpowerup.com did a nice table which shows at which resolution and on which RTX series graphics card can you actually use DLSS.
Metro Exodus is a bit of different story, as DLSS seems to work better there, offering different RTX improvements, mostly using it for realistic lighting and shadows, and not just reflections. The DLSS works slightly better in Metro Exodus, providing much softer images, and also offers up to 30 percent higher performance.
It also has limitations for certain resolutions and hardware to a way that it does not make a lot of sense and as you can see from a table made by Techpowerup.com, you still can't use it without RTX, unless you run the game at 4K/UHD resolution.
Both RTX effects and DLSS are finally getting enabled in some big games and hopefully, Nvidia will be able to push more developers to implement these features and eventually, as it obviously has certain advantages in both image quality and performance.