His speed wasn't enough as far as what?? When facing Raikage or Madara?? I don't know and neither do you. But as far as the threatening part its common sense man. If you think your facing a situation in which u feel superior using a basic move (being speed w/o fgt)why would resort to using one of your best techniques (fgt)?? In those events u mentioned he didn't feel the need to use fgt because there was not an obvious reason for him to use it. Why would someone use there best technique on a simple situation or when first trying to figure out a mysterious character?? And he did use fgt one high level opponents, I didn't see him run around them. O and he wasn't alone, Minato had a team there also they just didn't get involved. Regardless, as I stated I just think their speeds are different, nit taking away from neither character, but Minato would have to teleport in order to surpass Raikage, not saying Raikage is faster or the other way around.