The only time I can remember a third party game making a huge difference on a Nintendo console is DKC, and even then, it was kind of first party. But without it, the Genesis would have won that generation in the US and quite easily. DKC 1's reverence keeps declining every five to ten years or so because younger generations who weren't around then keep downplaying it, but there was never a time when a non-Nintendo-developed game had a bigger impact on one of their platforms.







