The roughness in texture comes from the nature of making a duplicate from an original. This is because most bootleg cases come from a mold that was made from original cartridge shell. Personally, I think some bootlegs often feel a little like worn sand paper- slightly grittier than the standard texture.

If you are not buying it online feel the plastic texture.

This stamp is not on bootlegs and I've never seen a legit Nintendo cartridge pre-DS era without them.

This is a QA stamp so that if there are any problems when a game is released to the public, Nintendo can identify the manufacturing source from within their assembly factories. If the cart doesn't have a caution label (like the handheld games) then it's pressed on the front label. You should see at least 2-digits pressed into the caution label on the back.

If it's a Nintendo cartridge, check the labels for an impressed stamp.If the cropping of the image is off, it's a bootleg. If the bootlegger could find a better image on, say, a poster, they would take it and then crop it into a similar graphic overlay for all of the traditional SNES and 'Nintendo Seal of Quality' notes. Compare the image to other legit copies and look at image cropping.Kid Dracula for Game Boy is one example I have in my collection.

Still, it is worth comparing against an image of a legit version because a handful of games actually had poor images. Most counterfeits use decent scans for reproduction labels, and the quality is more than obvious when you see it. Is it blurry? It's probably a fake if it is. Look for these qualities when attempting to identify counterfeit cartridges. There are a couple of tell-tale signs which actually seem common for just about all Nintendo, cartridge-based systems.

Video game cartridge cleaner