I agree that a successful revolution in 1905 would have been unlikely to produce something akin to the Soviet Union. It might have played out more like King John and the Magna Carta and eventually settled into a constrained, constitutional monarchy with the czar somewhat a figurehead.
In any case, assuming the changes affected policies somewhat like a communist Russia would, then it really changes the outlook for WWI. Russia would still champion serbs in the Balkans, but wouldn't likely have a treaty with France. Thus, Germany wouldn't be so focused on preparing for a 2 front war. This might, instead, lead to another Balkan war instead of WW I, while France, Germany, and (maybe) the UK might have some separate conflict with a different spark.