"The world must be made safe for democracy." - Woodrow Wilson
The irony of Wilson's quote is that WWI did not directly make the world safe for democracy. In fact WWI directly led to the rise of state socialism in the former Russian Empire with its evolution into the USSR, and the rise of fascism in Italy and Germany. From a European standpoint WWI bankrupted the continent and the subsequent reparations imposed on Germany led to, among other things, WWII. The worldwide Great Depression was a huge contributing factor to the rise of these ideologies.
In Russia, WWI was the straw that broke the Tsarist empire's back. The Russian people were dissatisfied with the prosecution of the war and the strain it put on the country contributed to the successful rise of the Bolsheviks. So WWI helped secure the communist victory in Russia.
In Italy, WWI had been a huge economic burden on the country and when the treaties were signed Italy was not given its "fair share" and they felt slighted which led to a fertile environment of nationalism for Il Duce ("Benito Mussolini") to eventually take office. Il Duce of course ushered in the Fascist government in Italy.
Likewise, in Germany, the German people felt they were too severely punished by post-WWI treaties. This like Italy led to an environment where German nationalism was high, but also in Germany there was severe hyper-inflation destroying the German economy. Hitler exploited these conditions to unify the people behind his idea of a "Third Reich" and lead the continent to war.
As far as democracy, after WWI not many nations around the world were democratic. The idea of democracy that we have today (with full suffrage, and robust elections) was not completely mature. It would not be until after WWII that democracy would begin to spread around the world. Really, democracy did not spread to the developing worlds until the decolonization period post-WWII when many colonizer nations simply could not afford their far flung empires.
So in answer to your question WWI did not do a great deal to shape the particular ideological beliefs of each particular system. However, the events of WWI set in motion the sequence that lead to a great deal of democratization.
I'm not sure if that exactly answers your question, because it appears that you maybe are looking for more of a political theory type answer than a spread of democracy type answer.