This battle right here.
As a gamer who grew up in the 90's, it was pretty much a given that I was a Pokemaniac, and so this final battle with Red seemed, to me, the logical conclusion of the series. I mean, after conquering both Leagues, what challenge could possibly remain other than him?
Looking back, it's a fairly straight-and-simple duel, if you go into it with a balanced team and a basic understanding of type advantages... But honestly, I was, like, 12 or 13 when I first played that game. My entire team consisted of Fire and Fighting types, and besides that, a duel with Red was the very last thing I was expecting to find on Mt. Silver.
Great fight. One of gaming's best, in my opinion.