I'm the kind of person that likes his cars to have ample power ( the smallest engine I've ever had in a daily driver was a supercharged 3.8L V6). But for the past decade and a half or so, four cylinders have come a long way. A year or so ago I ended up inheriting two vehicles, one of which was a 2008 Chevy Mailbu with the normally aspirated 2.4L I4, only 12k miles on it. It was perfectly adequate, it wasn't a rocket or anything, but it moved the car fine. They did offer a V6 with the 2008 Malibu, but I can see why original owner of the car didn't opt for it. The standard I4 was fine, and while the V6 would've no doubt been more powerful, I don't think the difference would've warranted the extra $2500 outlay for it.
The 4 cylinder Accord gets to 60 MPH in 7 seconds these days, the new Miata only takes 6 seconds to get to 60. And if you want low end torque, there are many I4's with a twin scroll turbo that will torque most larger V6's. The 2.3L Ecoboost can easily be taken up to around 390 ft/lb of torque with an air filter and a warranty-friendly tune.
With that said, I have V8 Mustang, a V8 F-150 and I6 Triumph. But if I had to commute 50 miles to work every day, I certainly wouldn't overlook something a like Focus ST or WRX. I have a buddy who has a 2008 Mustang GT, a 1988 Mustang with a 427W, a 2015 V6 Ecoboost F-150 , a 1992 Bronco, and a 1967 Bronco. But he drives a 2012 Focus as his daily. A four cylinder makes alot of sense for alot of people, I'd bet that most cars sold in the U.S. have had four cylinders for some time now.