Strange, von humboldt and Davis, but not de Ojeda, Verazzano or Vespucci. But, don't ever omit Columbus who stumbled upon the Caribbean and proceeded to wipe out all the indigenous people he could!
Bartholomew Diaz rounded the cape in 1488. Da Gama subsequently travelled to India (you gave 1497-9) and was the first to do it. If Diaz made it, it has to have been later.