The French striker will face off against Chelsea clubmate Hazard in Tuesday evening's tie at the Krestovsky Stadium.
Les Bleus have Mbappe in their ranks, meanwhile, with the Paris Saint-Germain striker becoming his country's youngest ever World Cup scorer earlier in the tournament.
Both players have been linked with a move to Real Madrid before the transfer window closes next month, and Giroud insists that they are "both geniuses".
"Mbappe is still a raw diamond to polish," the 31-year-old told reporters. "He is still very young and can progress hugely. He is more dangerous with his speed I would say. He is able to do some moves deep inside without the ball. Kylian is more of a striker than Eden.
"But to stand alongside Eden every day at Chelsea, he is impressive when he is driving with the ball, in his capacity to cut through with the ball. For me, he is one of the three best players I have ever played with in my whole career. They are both geniuses."
Giroud and Hazard are two of 17 Premier League players that could be on show in the semi-final clash between France and Belgium.