Engine character, power delivery, sound, reliability, serviceability, are all as important as power numbers.

Naturally aspirated high revving engines tend to excel in a lot of these areas.

To this day it still impresses me that BMW made a production 3.2l 6 cylinder in 2001 that made 333-343hp especially compared to other production naturally aspirated 6 cylinders at the time. I do realize that if the E46 M3 would have come out today it would probably be SAE rated at around 310-320hp but its still impressive for a stock 3.2l engine.

More advanced variable valve timing, direct injection, better/smarter fuel and ignition controls, way better manufacturing tools and techniques, and possibly the most important, better metallurgy and base materials.

Engines got more efficient, better exhaust flow and air intake, higher compression, if you look at the mustang with the coyote, it has an air intake coefficient of 100 to 110%, these are all little details that can optimize and get the most out of an engine.

Precision through computer simulations, take 2jz for example, a huge and over-built in every corner of the block, but it’s extremely heavy and inefficient especially being a cast iron block.

Modern engines are smaller, lighter where mass are only necessary added based on the engine’s weak points. Materials selections have also improved for better costs to strength.

The biggest technological change in most industries in the last 20 years has been computer software related. Same with the auto industry. Better computer modeling of the flow of gases in the engine (CFD) allow for better fine tuning of all passage ways and allows higher compression because of a better understanding of when the mixture will combust. Butter ECUs allow for better optimizing of the engine for different conditions (different loads, rpms, fuels mixtures, temporaries, etc). Better automation allows for more rapid iterations in physically testing everything which also resulted in an advance in material science.

In generally the biggest advancement on ICE engines on last 20 yrs are materials (lower internal friction), better control of mixture forming and burnign (better control electronics, direct injection, etc)

Not all of these advancement are nessarily for good in terms of durability IMO.

But for you question, take std.M54B30 and slap couple of turbos to it and it gives easy 500hp. Rebuild it to suite and you have more with reliabilty, so you dont need modern engine to make power, those turboes does most of the work.

The real freak is the Porsche GT3RS engine. All-motor 4 liter Flat six making 500 horses.

I don’t know what service intervals are like but the only things comparable imo are the LT6 and GT350 motor.

Turbos are less impressive imo because even in the 90s there were insane power levels from turbo charged engines, really even the 80s, it’s just that the power delivery got more linear with twin scrolls and sequential turbo systems.

There still is lag though. My M177 even lags sometimes. Rarely but it happens. NA motors don’t have lag but are generally peaky below 8 cylinders.

You have already named the big difference, and that is the turbo.

But comparing na VS na comes down to tighter tolerances and better fuel mixing for a more complete combustion.

Direct injection.

Advancements have come from materials, intake and exhaust efficiencies. Motor size doesn’t matter like it used to back in the day of carbs, the old way was crude and so inefficient compared to the modern stuff.

The gains with the modern stuff is so small and minor, a few hp here and there but over the course of decades it became impressive. Turbo’s were never really all that great until recently and they have so much room to go…plus hybrid systems, you’ll be looking at extremely quick cars.

Problem is EVs are taking over, so much faster and r&d into ICE is going to stop.

Imagine modern engine materials and controls with early 2000s emission regulations. Now that would be power

The G80 has two big turbos. A more interesting discussion would be around how powerful small engines have become, like the Yaris GR with a 1.6 and 500-600bhp some are running.

Look in to the LF4 engine design from GM. Lots of cool tech in that one.

The e46 m3 had a v8 or a v10 that made 500 horse or aomeshit lol.