I'm with canarias on this. It may seem like the Axis are much more powerful at the start in terms of available IC, but the advantage is not what it seems at first flush.
I usually play as Germany, 1933 scenario, and by the time war breaks out in 1939, things are pretty much as they should be. Poland puts up minor resistance and has a fair amount of troops, but falls in a couple of weeks. The Norweigans and Danish are no problem with only token forces (just like IRL). The Dutch and Belgians are merely a speed bump on the way into northern France (just like IRL). The French fight a determined resistance with ample troop levels but usually get defeated fairly quickly because of faulty/foolish strategy (somewhat like IRL). In more than a few games they focus nearly their entire army in the area just to the rear of the Maginot and up south of Luxembourg, usually trying to make a stand in the northeast of France while I swing in behind them along the coast and seize a virtually unguarded Paris. By the time I get to Paris, the French AI has only just begun to react and has started diverting forces from their pointlerss defense of northeast France to Paris and the lowlands. Too late.
The Brittish, however, do a marvolous job of garrisoning their island and making it much more difficult to pull off Sealion when compared to other HoI games (just like IRL). I have yet to successfully complete the invasion of Great Britain in IC.
Just like IRL, the Allied navies are much better, but their armies are severely anemic leading up to, and in the early stages of the war. However, as the war carries into the second year (just like IRL), troop strengths start to surge, IC has taken a massive leap forward, and combined, the Allies are easily out-producing the Axis. This is pretty much true-to-life.
At first I thought the Soviets were a little weak in 1941, like it was too easy to steamroll their defenses and storm Moscow, but then I realized this is exactly how it was in 1941 IRL. The Soviets had a huge army but had major morale issues, poor training, only about 1 in 3 men actually had a weapon, and ammo was in short supply. They were poorly prepared, and were easily routed. The only reason Moscow did not fall in 1941 IRL is because Hitler second-guessed his generals and ordered Army Group Center to the South in an "assist" rather than continue their push on Moscow. His gamble failed and they ran out of time; winter came a little early and very brutal and stopped the Germans cold. (Winter stopped them, not the Soviet army)!
In IC, this has been simulated pretty well by tweaking the TC. By the time October rolls around in 1941 and the Germans have taken Moscow and pushed further east, TC is stretched very thin and ESE becomes a major issue. Suddenly winter sets in and I start losing a lot of troop strength to attrition (not a shot fired...but cold as hell and terrible ESE, just like IRL). This gives the Soviets the long winter of 1941-42 to regroup, rebuild, and get ready to launch effective counteroffensives in spring of 1942. Only this time, the Great Patriotic War has fired and their GDE has gone up and they are fighting much better. Most of their IC was moved to Siberia, so their industrial base is still fairly intact (even after pushing all the way to the foothills of the Urals, the SU still had close to 300 IC).
By this time, the US is in the war and is starting to build up across the Channel in England and is harrassing the hell out of western europe via its navy and airforce. Then Darlan cuts a deal with the Allies and suddenly, they're pouring into a relatively undefended northwest Africa. Now I am fighting on two fronts and the Italians and the minor Axis powers are all but useless protecting the soft underbelly of Europe (I prefer to leave military control to the minor Axis powers as I feel this gives the AI and the Allies a better chance...they've already got me as Germany to deal with...they don't need me also controlling Hungary, Romania, Bulgaria, the Spanish State, and Italy...they would never stand a chance).
By 1943, things are pretty interesting, and it is by no means a given that I will win. Usually, victory is only assured for me if I can knock out the SU by the winter of 1941 (damn near impossible...especially with the revamped TC), or, at the latest, by late spring of 1942. If I am still tied up in Asia by the time the US starts firing up in the Atlantic and European theaters, it can get pretty hairy (again, as long as I resist the urge to take military control over the rest of the Axis).
So, I am with Canarias on this. The game can be quite interesting if you let it be. And the devs have done a pretty good job with trying to simulate the real life challenges faced by each side during WW II given the limits of today's AI capabilities.
I say "kudos" to the devs and enjoy the game. We're still quite a few years away from being able to implement the kind of AI that would be as challenging as another human being, and we'll probably never be able to "program" the subtleties and intricacies of real life (unless someone spends their entire life doing just that).