My gaming circle does not feel Axis and Allies WWI is balanced. None of us has yet achieved victory as the Central Powers. What rule modifications would you suggest to balance the game?
The standard way to create balance in Axis & Allies is to use secret bidding. For example, bid an amount of money that Germany would get extra at the start of the first round of the game (the one bidding lowest gets to play Germany).
For example, two players bid in secret. Player A bids 20 and player B bids 25. This means Player A gets to play the Axis and that Germany gets an additional 20 IPC the first round. The rest of the game unfolds as normal and Germany does not get additional money in later rounds.
The upside with this bidding is that nobody can complain that the game was not balanced any longer (if they thought differently they should have bid differently).
I would make the following observation, that there are THREE blocs (not two). They are: Central Powers, Germany, Austria-Hungary, Ottoman Empire, 77 IPCs; Western Entente, Britain and France, 54 IPCs; "fence sitters," U.S., Russia, and Italy 59 IPCs, in total. Although aligned with the Entente, the fence sitters basically had the balance of power. So game "fixes," might be addressed at them.
Russia: Make it easier for the Central Powers to start the Russian Revolution and knock Russia out of the war by conquering Poland and one territory adjacent to Moscow (instead of three), or a total of three territories not adjacent to Moscow. That eliminates Russia's 25 IPCs. Also, the Central powers get to keep with their IPCs for the conquered territories.
U.S. It's not a given that the U.S. joins the war. One might make a rule that beginning with turn 3, the Western Entente gets an "allowance" of 10 (out of 20) U.S. IPCs per turn, delivered to the UK. The Central Powers can permit this, or else they can "interdict" those IPCs, by declaring unrestricted submarine warfare. Beginning with the turn on which "interdiction" occurs, the U.S. player may join the war on any turn when in rolls a six, but it can build units only U.S. territory. Sensible Central Powers players would often opt for the 10 IPC allowance.
Italy: Italy didn't make a decision (in real life) until 1915. At that time, force both sides to "bid" for Italy's services, using IPCs. The Central powers had the advantage, insofar as they bid for Italy (in real life) using Austrian territory (specifically Tyrol). The Western powers can outbid them by offering Tyrol and Trieste, but if they don't "pay off" by controlling those territories at the end of X turns, Italy re-joins the Central powers. If the Central Powers capture Venice (as they nearly did after Caporetto), or any other Italian territory, Italy goes back to being neutral, minus its lost province.
The "fence sitters" can win if their IPCS of 20 (U.S)+ Russia (25, minus Central power occoupied territories)+ Italy (14IPCs, plus territories handed over in the bidding war) exceed that of both the Allies and Central Powers.