I agree with Birgila -- I also see "standard of living" and "quality of life" as two separate concepts. The first is something we could measure, if only we could agree upon certain benchmarks -- potable water, indoor plumbing, percentage of children attending school, various health measurements, hunger, illiteracy.
Quality of life is something I see as much more subjective. Someone in deep Bavaria, living far outside of town on a dirt road, raising a few cows may feel his quality of life would be REDUCED by living in a big penthouse in NYC, with shopping available 24/7, theaters on Broadway showing the latest shows and all the amenities of city life at his doorstep.
I have a feeling that the 'average' US household has a lower standard of living than the 'average' German household based on the standards I mentioned above. I'm considering the overall small number of very rich American households, the shrinking middle class and the growing number of homeless and what is now called the 'working poor' -- people who have a job, or maybe even two, but can't make ends meet. The average German household seems to fall higher on the standard of living scale, if you take the entire population of each country into consideration.
On the other hand, families which would be considered 'middle-class' in the US seem to have a much higher standard of living than what would be considered a German middle class family.
I grew up in what most would consider a normal middle-class suburb (of Chicago). Both of my parents worked, we owned multiple cars at any one time, had various mobile homes over the years, a large house with five bedrooms and two full baths, there was a pool and a fish pond in our one-acre backyard. Every bedroom as well as the family room had a TV. The living room was separate from the family room, with a fireplace. There was also a formal dining room.
The kitchen had all the gadgets and small appliances most US families take for granted (Cuisinart, blender, toaster, toaster oven, etc), as well as a large oven with large rangetop (much bigger than the standard German stove), microwave, full-sized refrigerator (again, much bigger than your average German fridge), the separate deep freezer.
We shopped at the normal neighborhood grocery store -- large beyond belief compared to German grocery stores, with many more products overall and much more selection in each area. Cleanliness, lighting and space are a given in most US grocery stores.
We vacationed all around the US, visited Canada and also made regular trips to Germany to visit family (every two years or so).
Other families in the area that didn't travel as often as we did often had newer cars or an expensive family hobby (sailing, water-skiing/motorboating, etc).
I find the average middle-class German family lives a much more spartan life. (Again, this is just my impression.) Maybe one or at most two cars, a smaller home or perhaps an apartment, smaller rooms in the home, no air conditioning, rarely a pool or large yard, smaller appliances, etc. Many of the 'extras' of US life seem to be 'missing' -- a phone extension and TV in most rooms, the many small appliances in the kitchen, the nice, large, full-service grocery store down the street, the full fridge and separate freezer.
But, the German family has the advantage of many more smaller specialty shops, less expensive higher education for the children, a greater number of interesting foreign travel destinations nearby, a much better public transportation system to get there with, etc.
All this being said, I think that the decision whether the German or the US lifestyle is the one that would improve YOUR quality of life is something that only YOU can decide.
(Sorry, I didn't mean for this to get so long! The topic is something I've been thinking about lately -- I'm moving back to the US in January after nearly two years in Germany.)