Re: Making a Super Nintendo Remix
If you have money, Super Audio Kart for Kontakt is probably the best you can get in terms of a comprehensive sample library of SNES stuff.
As far as free options go, many SNES games have soundfonts, instrument banks that have been extracted from a game's files. A lot of popular SNES games have soundfonts you can download and load into any sampler VST. Even if there isn't a soundfont out there for Contra III, looking around for SNES soundfonts should yield something close.
One other thing, SNES has a very particular and distinct type of reverb, and usually lots of it. There's a VST called JBM Spacer you can download for free that emulates SNES reverb, if you're going after that type of sound, I would definitely put that on every track.