"of WWII" meaning it was used at that time? The 1911 is certainly the most successful individual small arm that was used in that war from a commercial-success standpoint. I'm not saying it's the most effective force-multiplier or most effective weapon, but if I were to pick a winner based on which patent I'd want to own, it would be that one. All the others are relics. All of them. The Garand, M1 or M2 Carbine, the K98, the Thompson, the grease gun, the Sturmgewehr, the Luger, the P-38, are all just relics today. We could say the Stg. 44 was the father of assault rifles, but it's hardly the same thing as the AK-47 or AR-15. The K-98 is really the only other design besides the 1911 that continues to be used in practically the same form, just with sporter stocks and tapered barrels.
Which was the best one to have an army equipped with? The Garand.
Which was the most innovative and futuristic? The Sturmgewehr and the P-38.
The M1 Carbine has to be given credit for making an outsized difference and could even be credited with engendering the genre of lightweight, short, semi-automatic carbines that are so popular today (as in semi-automatic AR-15's with 16 inch barrels). If the M-16 A1 had not been given a lot of M1 Carbine features, AR-15's wouldn't be nearly so popular today.