Final Fantasy IV
Well, it certainly gets no points for imaginative naming. "Main Theme" is even worse than "Clash on the Big Bridge." But it is, I suppose, considered the theme music of Final Fantasy IV; I remember it as the overworld map music. And there has never been better overworld map music. Every Final Fantasy game after IV had progressively weaker overworld music, in fact, with the sole and regrettably brief exception of the genuinely creepy pre-Falcon World of Ruin music in Final Fantasy VI. (Which just missed this list.)
I think this track was one of the very first to open my eyes to the idea of "holy crap, video game music is awesome!" And the more you play Final Fantasy IV the more you realize what good theme music for the story this is.