I happen to own a copy of Super Mario Bros./Duck Hunt. I also own the NES, Famicom, Famicom Disk System, and SNES (if you count Super Mario All-Stars) of Super Mario Bros. but they don't have Duck Hunt included.
I own Super Mario Bros./Duck Hunt on the NES too! I wanted wanted to get the combo cartridge so that I could use the Light Gun, haha. I bought the game used off amazon and it still works! Love this classic.
These are the games of my childhood, it brings a lot of nostalgic moments back. I think the fact that Mario games will bring joy to other generations too, but now the graphics are far more sharp, 3D engine, and alike