What is the main message of the resurrection for modern day liberal Christians?
I think there are as many views on this as there are "modern day liberal Christians." And, for semantics, most of us today would probably view ourselves as "post-modern", meaning, later than the modern, fundamentalist age of the late 1970s-1990s. I see the message of the cross of Christ as the ultimate message of life over death - that life can be found in death, and that we have hope to die to a sinful nature in ourselves and be "resurrected" anew spiritually.
I find the idea repulsive that Jesus would die as a human sacrifice for our sins; that idea is as primitive as a tribe burning babies to the gods.
I don't think the message of good over evil is a message of the resurrection in particular, although maybe a subtext. Although the idea is popular that during Jesus' three days "in the grave" he conquered hell, there is no basis for this is literature or tradition. That Jesus will finally conquer over evil in the end days maybe another myth/story to consider.
To my knowledge no other religion has elevated a man above or on par with its message.
What about Buddhism and Islam?
IMO I find it very easy to see how ancient and primitive people actually had CLOSER relationships with God than most do today. People of those times, firstly, didn't have the distractions that we find in today's time nor the "hustle and bustle". Secondly, they did not understand the world around them as well, which actually required them to trust God even more.
I think it is more likely that people needed God to explain things that science could not explain. How did the sun come up and go down every day in the same interval? OH, God makes it rise and set. It was heresy when it is first discovered that the earth is turning and the sun is (relatively, for this argument) stationary. Where did humans come from? God created them from the dust of the earth. Then we have Darwin that comes along and leads us to a scientific explanation for the origin of humankind, and voila, another reason to use God to understand the natural disappears.
I think this is why so many Christians fight like the third monkey on the deck of Noah's ark to defend creationism -- they fear that if they let it go, then the need for God will disappear. This is simply not the case, but it is this fear that drives fundamentalists to these types of anachronistic beliefs. Christians--we have to live and understand God and our model and savior Christ in the light of the 21st century!