Warning: Long post...
I'm not sure what you're referencing when you say the Malibu V6, since the V6 was last available in the Gen7, model years 2008-2012. In the early years of the Gen7 it was possible to get a choice of the 3.5L pushrod (mostly for fleet orders) or the 3.6L DOHC. In earlier generations, the 3.6L was not available but there were other sizes, such as 3100, 3400, etc.
The V6 engines prior to the 3.6L were pretty decent, but the older you go the less HP per CC there was. They were also less fuel-efficient but still better than many earlier offerings. As to power, I can't speak as I never drove any, so it would just be a paper race.
I have owned 3 different Malibus with the 3.6L engine. I still feel that my 2009 was noticeably more powerful and efficient than either of my 2011 models proved to be. In September 2015 I took my 2011 to a ¼-mile dragstrip in Maryland. Temps were above 80F and the humidity was fairly high as well, and it was my first time ever on a dragstrip, but with guidance from a buddy I was able to make 5 runs that turned out to be fairly similar. I turned in times at 14.9 or less and did so with a full-sized spare tire and a bunch of stuff in the car equal to another person's weight. With lower temps and humidity and being able to trim 200 pounds (or more) of contents from the car, I think it could knock another tenth or two off those times.
The affordable, mainstream "muscle cars" of the 60's were rarely able to do a similar job. It took special packages or modifications to do so, so I'm comparing an affordable mainstream grocery-getter (2011 Malibu 3.6L DOHC) to a more-or-less average car like it from the 60's.
So, now that we have set the stage to at least
try to compare apples to apples, let's just agree to say that new vs. old ends up a pretty close match, regardless of which one actually comes out on top. But, if anyone wants to belabor the comparison further, that's fine, too.
Now let's compare fuel mileage. The old cars, even with the smallest engine possible (remember, mid-sized cars, not econo-boxes), you might be able to get 25-30 mpg on the highway and close to 16 mpg around town. These engines are either a straight 6 or a V6. My 2011 3.6L is rated 17 city and 23 highway by the EPA. I get around 20 city and 25-30 highway. So, does that mean that I have an economy car? No, it means that I can meet or exceed the fuel mileage figures achieved by the smallest engines while still turning in ¼-mile times on par with larger engines of the 60's.
Comparing fuel mileage of the larger engines of the 60's turns out to be what looks like an exercise in futility. Many of those "ground-pounders" could barely get 20 mpg highway and 10-12 in town. And we're not talking the huge engines that came in the fastest cars of the time, we're talking engines like the 283, 289, 302, 305, 327, or 350, maybe even the 383. (Not sure all of those were available in the 60's but you get where I'm going.)
What kinds of HP numbers were being advertised by manufacturers of the 60's with those medium to large engine displacements? Somewhere between 150 to 300, depending on engine size and options. Taking a look at that you'll notice that the technology of the 60's meant displacements were about double that of my 2011 V6 just to be on par with the HP, yet none of the engines that can be considered for comparison are within 50 cubic inches of my V6, and all of them are still V8 engines. Just so it's out there, the 3.6L V6 is rated 252 HP on paper. I don't know what it puts to the ground as measured on a dyno.
Last but not least, let's talk handling, as in emergency lane changes or just road-course slaloms and backroads in general. I had my '09 doing about 100 mph when I had to negotiate a bend (not a turn or curve, just a small bend) to the left that also had a small dip in it. It unnerved my passenger and me enough that I had to slow to 80 for the rest of the corners on that road. At lower speeds more akin to normal driving, this car does remarkably well even though it's not set up to be a race car. Harken back to the any domestic American car of the 60's, 70's, or even 80's and you'll admit that they earned their nickname - "Land Yacht". Take any corner, even at low speeds, and the body rolled enough that it was like a boat, but in the wrong direction.
So, let's put this in a chart that's easier to understand:
Time period . . . . '08-'12 . . . . . . 1960 through 1972-ish
Engine size . . . . . 3.6L V6 . . . . . Straight 6 . . . . . V8
Fuel mileage
. . . Highway . . . . 25-30 . . . . . . 25-30 . . . . . . . 16-20
. . . City. . . . . . . . 17-20 . . . . . . 14-18 . . . . . . . 8-13
Horsepower. . . . . . 252 . . . . . . . . 90-120 . . . . . 150-300
Cubic Inches . . . . . 217 . . . . . . . 170-230 . . . . . 262-383
¼-mile times . . . . . 14.9 . . . . . . very slow . . . mid 14's to over 17
Handling . . . . . . . . decent . . . . . . fair . . . . . . . . miserable
My opinion is that current technology makes more power on less fuel from a smaller engine, and the overall handling is much better. But when it comes to styling and just the overall Wow! factor, the 60's have it hands down. I like my 2011 but those older cars are highly desired, and the styling is a large part of it.
My final comment: If you'd like to compare apples to apples I agree, otherwise we're comparing Apples to Androids!