Hybrids are a nice idea, but ultimately doomed to fade into oblivion. Their batteries are low capacity so most of the time you will run on the normal petrol engine.
Some diesel cars have lower fuel consumption, like the lupo with over 70 mpg. Next year, VW will start a small production sale of their 1L car, a 1 cylinder diesel, which as the name implies, needs less than 1L/100km.
But the future belongs to electric vehicles (if they implement the newly developed technique that enables batteries to be charged within minutes) and most importantly hydrogen powered cars.