I'm sorry, I've had to delete this thread before it turned into something more akin to an AskReddit or /r/History thread than what we'd like to have here. Your question is perfectly fine, it's just that it's a very loaded question for some and that leads to less experts wanting to answer and more people who have no clue about WWII wanting to chime in.

There is no absolute in history. There is no 'most important country' in WWII either. It was an allied victory where each and every country played their part in the final defeat. To say that the western front or the eastern front was the most important one is rather irrelevant for historians. Soviet manpower, American equipment and British courage is usually said to have won the war - but there were so many other countries that contributed to the final win that picking one would be rather silly.