"The first impression is the one that matters."
I'm not sure if there is a proper "first meeting" between them during the pre-Crisis era (feel free to enlighten me about it), so I start with Byrneman and Perez's Wonder Woman from the 80s. As I already summarized here, sparks flew when Superman and Wonder Woman met for the first time fighting Darkseid's Hounds of War and couldn't stop thinking about each other.