Giroud hit a double in their FA Cup win at Brighton.
Wenger told arsenal.com: "He [Giroud] started a bit sloppy and became stronger and stronger. He finished the second half [in a] very, very good [way]. When he gets into the fighting mode it is difficult to handle him. This guy is tall, strong and quicker than people think he is. He has good finishing as well.
"He could have played in England 20 years ago, 10 years ago and today. He is all you need to play as a centre forward; a physical presence.
"He gives us something different. I believe with him and Theo we have a good blend. Without him today it would have been difficult.
"I knew before the game [it would be a test of character]. But we responded well I must say, especially in the second half."