I think among some fans, part of the appeal of futbol is that it isn't something steeped in our culture the way baseball and football are. Which is one reason we have eurosnobs (guilty) and supporters groups trying to astroturf European traditions in the stands. Even as a kid, I remember being delighted at the way soccer teams that I casually heard about were named. "Crystal Palace? Nottingham Forest, like in Robin Hood?"
I think there's another reason why soccer (and hockey) are exciting in a way that I don't find football consistently exciting. And it somewhat counter-intuitively has to do with scoring. The conventional complaint in America is that soccer is boring because it is low scoring. But in soccer, a goal can come at any time. It's pretty much always a surprise unless it's a PK. In football, a lot of scores seem inevitable. They come at the end of long, methodical drives. So they punch it in at the goal line, run a fade, or make a kick. It's scoring, but it isn't exciting in the way that a long score or a pick six is. Maybe not to the extent of basketball, but scoring in football doesn't feel special.