Metal Slug XX is a revised and expanded edition of Metal Slug 7, which took the original Nintendo DS game and bulked it up for an Xbox and PSP release back in 2010. On January 31st, the run-and-gun 2D shooter was added to the growing Metal Slug library on Steam, but the response hasn't been great.
It's sitting on a Mostly Negative review rating, with players highlighting problems with the port like a lack of graphics options, no way to rebind the keys, and the fact that pressing Escape closes the game without warning (you're supposed to use Ctrl to go back a step in the menu instead).
Even if you're playing with a controller the inability to change resolution—especially when the trailer highlighted its "1080p and 4K compatibility"—might be a frustration, and several of the reviews highlight "input lag" as a concern as well. Maybe hold off on this one.