the hydrocarbons in a nitrogen/methane atmosphere would definitely be an alien brew.
One of the current problems is that we only have one sample of life right now. So it's pretty hard to say what general conditions are needed until we get a few more samples.
One open question is whether we would be able to recognize life it was significantly different from the one sample we do have. We even have trouble finding the line between living and non-living within the forms that we do know about.
Aslan is not a Tame Lion