I dunno. A V6 may develop the same power as yesterday's V8's but it doesn't sound the same, although with today's variable valve timed, balance shafted, high output engines, the V8's have lost the sound they used to have.
It used to be Inline 6 engines that powered luxury cars, now, its V8 engines that can be found commonly in Mercedes and high line BMW cars, even Jags.
I still would take a V8 if I could afford the gas, although the mileage is usually close...
The other point is that the American Clover (uh, I mean driver) doesn't need the power of most 4's nevermind the V6 or V8. I lived for years with 4 cylinder cars and drove them faster than most do in their V8 Corvettes. With higher speed limits, that has changed some, but not much. 4 cylinder cars are just simpler to maintain. I just wish that a carmaker would make an inline 4 with rear wheel drive at a practical price.