Like others have already said the comparison is quite impossible. Especially Barbarossa is difficult to get on the scale with the two others.
Bagration and Overlord perhaps are easier (both operational and contemporary) and we could first try and see how the two forces would perform each others tasks.
Bagration crosses the English Channel and liberate Paris by late August: They can try an invasion like a river crossing on steroids. That was how the Germans (another land power) saw it in 1940, but against a much less prepared enemy and will anyway only have small and undersupplied forces across. Bagration is simply is no good at Overlord.
Overlord anihilates Army Group Centre by late August: All the effort put into landing craft will be wasted (but who cares when you have USA), but the 2 million men available for Overlord (N.France) actually outnumber Bagration by some 300.000 and will not stand back firepowerwise.
The W.allied armies in general weren't as battlehardened as the Red Army by 1944, but will anyway be so superior to the over stretched Army Group Centre that they stand an overwhelming chance. Considdering how the W.allies tricked the Germans at Overlord I guess they have at least as good a chance to deceive the Germans as Bagration had.
Regards
Steffen Redbeard
If you count those 2 million you are really comparing the 2nd front with the whole eastern front.