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Gotta go with Donkey Kong Country.
In 1994, it was beyond huge.
Visually, it felt like if a Crysis had come out on the Gamecube in 2004 looking just as good as PC. It truly felt like a next gen game that you could play on your current gen console. What's more, its visuals weren't just flashy, but richly moody and stylish as well.
Then there was the soundtrack. Again, there was absoluely nothing else quite like it at the time. It stood head and shoulders above the vast majority of gaming soundtracks and had a level of uniqueness and atmosphere that was just incredible.
All that was impressive enough, but even if you stripped away its phenomenal presentation, the game itself played like a dream, with tight controls, clever level design, and tons of variety.
It was the full package, a blockbuster that impressed on every level, and the impact it had at the time is hard to overstate.
