That just looks like an overlay image with a semi-transparent border. No actual reflections at all. Possibly a light blur on the semi-transparent edges.
Yeah, if you look at a screenshot of NSMB, the edges of the screen are much closer by comparison. Look at the coin and timer, they're very close to the 'edge' if the border was a reflection, but if it's just semitransparent they line up with a normal example gameplay image.
(edit: I am mistaken, this is a shader effect from an emulator. There is no shader like this for general OBS usage, no. You could likely just create a duplicate, slightly enlarge it, add a blur, and add an overlay image to get something semi-close though.)