Interesting experiment NWSRG, but in reality it's only of limited, if any, relevance. Aircraft designers
generally design aircraft to be as powerful as they need to be, as this has an impact on the economics of the aircraft.
Here are some notional examples why that might be the case. They are illustrative rather than scientific.
More power is good, right?
Well, not necessarily. Let's say we took an airframe and we put on a tiny turbojet engine, just enough to get the aircraft airborne and into the cruise. The engine weighs, for example, 1 Smidgen. The aircraft flies, cruises, descends and lands. Life is good.
Let's take the same fuselage, and attach four big turbofans to it. Let's say each turbofan, being a big beast, weighs 10 Shedloads each (40 in total). That means the aicraft is now significantly heavier and more powerful than before.
The problem is that because the aircraft is heavier, it needs to generate more lift to support its weight in flight. Lift has a bitter/sweet relationship, like many things in life. If you eat cream cakes, you will get fat. If you smoke, you will get cancer. If you need to create more lift, you will also create more drag.
Assuming the only difference is the engines, more lift would be obtained by flying faster. This means using those powerful engines to their potential. But more lift means more drag, which reduces efficiency. More power also means a higher fuel consumption, which means you need to carry more fuel. More fuel means more weight. Which needs more lift. And creates more drag. Etc etc.
In reality, design engineers have to carefully balance the various characteristics of an aircraft to ensure that everything is in equilibrium. There comes a point where a bigger, more powerful engine would end up actually being counter-productive -- it would weigh too much more, drink too much more fuel, and therefore cost more.
In our example, if an engine that weighs 1 Smidgen provides enough power to do the job, why put on anything bigger?
Extra power is a waste...
In commercial aviation, if you have more power than you need to get airborne, you don't generally use it.
In a light aircraft, once you get lined up, you open the taps and hurtle down the runway at the speed of paint. Life is good.
Jet aircraft don't generally do this. If you have a runway that is 5000 metres long and taking off at full power would get you airborne in 1000 metres, you would generally elect to apply less-than-full power during the take-off. This uses more runway, and also generally uses more fuel. So why do it? Well, engines can be expensive to fix so they tend to be operated with as much sympathy as possible. A reduced-power take-off, using only the power that is
really necessary to do the job, saves wear-and-tear on the turbines and prolongs engine life.
Therefore on a 757 'pocket-rocket' you may find that the crew fly reduced-power T/O's a fair bit.
Jet operating efficiency
Finally, jet engines operate at their most efficient when they are generating about 90% power. If you have a very light airframe with very powerful engines, you might find that (at cruise altitude) you only need 50% power before you hit your limiting top speed (known as Mmo).
This means that the engines are running off-optimum. This costs money. Ergo, more spare power available is not necessarily more good.
This is also the reason why some military aircraft, e.g. the Nimrod in the UK, actually shut down an engine when they are on-station. Doing so means the other three can be revved up to a more economical cruising power.
The bottom line?
Well, the bottom line is that manufacturers generally equip aircraft with engines that are powerful enough to do the job, and not much more. Remember: they are designing commercial aircraft, not hod-rods. These things are designed to make money, not burn it.
There is, evidently, some variation between aircraft and manufacturers. If you do a search on other forums, you'll find that Boeing have in the past been slightly more likely to put 'a bit extra for Mum' into the engine selection they offer on each type, giving them slightly more spare power. Airbus, on the other hand, jokingly get slagged off for being slower in the cruise and by seemingly climbing only by virtue of the curvature of the earth. Yet they are often identified as being more more economical in the cruise than some older Boeings.
The A380 designers will have looked at their aircraft. They will have looked at how economical the airframe is, looked at the airfields it's likely to use (along with their altitudes and temperatures), looked at the speeds and altitudes they'd like it to cruise at, and worked out how much power they will need from the engines. While it may seem underpowered according to your stats, it will (in theory) deliver the economies they are looking for.
Power-to-weight ratio is an interesting stat but it needs to be considered in context, most airlines wouldn't be worried about it and would be more concerned with 'operating cost per km' and similar figures.
HTH
Charley
p.s. have you noticed, as an aside, how your list seems to be in order of 'long-haul' to 'short-haul'? Think about it...
