Why isn't efficiency part of a BEST ENGINE?

In response to
Ward’s 10 Best Engines Reviewed (Mostly)
Posted by: Matt Vella on December 07 at
http://www.businessweek.com/autos/autobeat/archives/2006/12/wards_10_best_e.html

I left the following comment
right at the end of cheaper gas...

John Acheson
December 28, 2006 12:16 AM

What are the metrics for best? I'd like to argue that it should be one metric, efficiency. For every 10 gallons of gas, most engines burn up 7 or 8 right? Why aren't we measuring this? Why isn't it part of being a "best engine?"