From my own understanding, the bigger (and heavier) aircraft, the higher approach speed it needs to keep itself from stalling. According to this site, the approach speed of an A380 is 140 knots, and 160 knots for a 747. In contrast, the F-16's landing speed is 141 knots, and 135 knots for the F-35C.
Doing mass-to-speed ratio, it doesn't make any sense to me. Could you explain why do fighter jets land faster while they are lighter than large commercial aircraft?
It is not only the mass that affects the landing speed. Wing area plays an important role as well.
A larger wing can lift more weight at the same speed than a smaller wing. If you compare the wing loading of these aircraft the differences are smaller:
A388:
B744:
F-16A:
Landing speed varies depending on several factors.
For airliners you have to take into account that the wing airfoil is radically different than the wing airfoil from a fighter jet: airliners have flaps that modifies the airfoil and doing so the lift and trail (not sure of this word in English) modifying the speed range of the wing (reducing the stall speed) and so allowing slower speed for landing.
In the case of a fighter jet the wing is in general a delta wing without flaps, so in order to reduce the speed for landing they have to increase the angle of attack to augment the trail without loosing too much lift. That why in this phase they cannot lower too much the engines and the speed, because their wings are not suited for low speeds. If you look at the Concorde (a good example of delta wing) they had to put down the nose during landing phase to be able to see the runway because of the high attack angle requested to be at the right speed (about 180-190 kt).
Because they are lighter, they have less kinetic energy so there is less to dissipate. This is easier on the brakes. Remember kinetic energy is $E_k=\frac{m \cdot v^2}{2}$.
Also fighter jets aren't as good gliders as jumbo jets. This sacrifices lift for maneuverability, so they have better acrobatic performance. While airliners will spend most of their airtime going straight ahead at high altitude so they benefit the most from being good gliders.
To simplify, the differences are similar to comparing a dart to a glider -- it all gets back to the wings.
The delta wing provides the best overall flight characteristics in terms of lift and control surface efficiency. A delta wing will allow you to come in low and slow and in control, but is that always what you need if you are flying a fighter jet?
The aerodynamics of fighter jets are designed to provide lift, stability, and control at a much wider angle of attack. Comparing the wing characteristics between the two planes in a wind tunnel, notice how the wing thickness (airfoil) of the fighter plane is much less (relatively flat) at the leading edge.
Although the fighter plane provides less lift at the same angle of attack and requires a faster airspeed to stay aloft without stalling, the control over a wider range of airspeeds is worth the tradeoff for the fighter jet performance and maneuverability.
Shut down a fighter plane engine, and it will drop like a yard dart. The intake on a fighter plane is designed to receive as much air as possible, and will cause turbulence at the inlet if the blades are not turning fast enough. There simply is a minimum speed range to keep the plane in flight and under control as it is coming in for a landing.
The power to weight issue has a downside -- the fighter plane is less efficient in fuel consumption -- it is even less efficient if the inlet has nacelles or ducting to mask a thermal signature.
The power to weight ratio of the fighter plane is much higher than a commercial aircraft, and the answers above from the other posters regarding thrust cover the topic well.
The best fighter jets provide the most maneuverability over the widest range of speeds.
Both types of aircraft would technically benefit from a lower landing (and stalling) speed, but in both cases, other flight characteristics are a higher priority.
Here's another factor in approach speeds - the military fighter/trainer aircraft I flew used 1.2 Vso (20% above landing configuration stall speed) for approach. Airliners are required to use 1.23 Vso and each model uses a different multiplier which often changes with different flap settings. The previous generation 727/757/767 mostly used 1.3 Vso while the newer airliners use 1.25-1.28 Vso. That difference reduces a fighter's approach speed by 4-8% vs what an airliner would use. Light airplanes use 1.3 Vso, or 30% above stall speed, for their approach speed.
