The SBD is the only contender at that is as much due to being in the right place at the right time as any intrinsic qualities of plane itself.
The Yak-1 and IL-2 only come into play because they didn't suck as bad the I-16 and SU-2.
This has been mentioned a few times before, but I am not sure I agree.
The SBD may not have stood out in any obvious specific merits by which WW2 aircraft are typically rated - it didn't fly 400 mph like the Mosquito and it didn't carry 10,000 lbs of bombs like the Lancaster, didn't carry 8 x .50 cals like the P-47 or 4 x 20mm cannon like the Fw 190, and it didn't fly 2,550 miles like a Wellington. But for it's era, it was close enough to excellence in many different measurable criteria and others which are harder to define that I would say it
was actually an excellent design with intrinsic qualities that made it a war winner.
The primary characteristics needed by a bomber are bomb accuracy, bomb load, and
Survivability. Of secondary but still significant value were versatility, lethality, and viability.
Bomb accuracy means how likely are bombs to hit the target.
Bomb load is obvious, how many bombs and of what size can be carried to the target.
Survivability means the intrinsic qualities of the aircraft the contribute to it's survival as a machine and the survival of it's aircrew.
Secondary traits - versatility meaning how adaptable was it to various intended and unforseen missions besides the original design specs.; lethality meaning how much damage did it cause to enemy aircrew and ground targets aside from the effects of dropping ordinance, and viability meaning how often was the aircraft actually working and available for combat. Could it operate in difficult conditions, was it subject to chronic maintenance problems, was it hard or easy to repair.
A lot of people emphasize bomb load over all other traits in a bomber but I think it's actually the least important for most missions, beyond a certain critical point. For a naval bomber like a Dauntless there is a minimum weapon size needed to damage a large warship, i.e. by the time the Dauntless was in action roughly a 500 or 1,000 lb armor piercing bomb. But beyond that minimum, accuracy was
far more important. Dropping 10,000 lbs of bombs in the ocean is basically useless at damaging a ship (unless you get a near miss). The mentality of a bomber as a 'bomb truck' is really what cost us the War in Vietnam. During WW II, bombers were notoriously inaccurate. It was not at all unusual for medium and high altitude level bombers to bomb the wrong city. Bombing at night made it even worse.
Tactical bombers required accuracy more than anything. Relatively small ordnance could knock out a tank or gun position, but
inaccuracy could mean killing your own troops at worst, and having no effect at all at best.
More than one battle in WW2 saw bombers causing massive casualties among their own troops.
In naval combat the Strategic and Tactical are combined. The target, a ship, is tactical, but the results (i.e. sinking Carriers, Transports, or Battleships) are potentially Strategic.
So a single day's action can be decisive. This means accuracy and bomb load are more important than all other factors for a given action. In this respect the Japanese D3A and B5N bombers were equivalent to the SBD. Both were lethal ship killers. For comparison here are all the single engined bombers I can think of from the early part of the war:
D3A1 - range 800 miles, speed 242 mph, guns 2 x 7.7mm and 1 x 1.7mm defensive, bomb load 1 x 551 lb and 2 x 132 lb bombs. Dive bomber = Yes
B5N2 - range 1,200 miles, speed 235 mph, guns 1 x 7.7mm defensive, bomb load 1 x 1760 lb torpedo
SBD3 - range 1,115 miles, speed 255 mph, guns 2 x 12.7mm (offensive), 1 x 7.62mm (later 2 x) defensive, bombs 2,250 (usually one 1,000 lb AP bomb). Dive bomber = Yes
JU-87B - range 311 miles, speed 242 mph, guns 2 x 7.92 (offensive), 1 x 7.92 (defensive), bombs 550 lbs bomb plus 4 x 110 lb bombs. Dive bomber = Yes
TBD Devastator - range 435 miles, speed 206 mph, guns 1 x 7.62 or 12.7mm mg (offensive), 1 x 7.62 mph, bombs 1,000 or 1 x torpedo
TBF Avenger - range 1,000 miles, speed 275 mph, guns 1 x 7.62 (offensive), 1 x 12.7 and 1 x 7.62 (defensive), 1 x 2,000 lb torpedo
Swordfish I - range 522 miles, speed 143 mph, guns 1 x 7.7mm (offensive), 1 x 7.7mm (defensive), 1 x 1,670 lb torpedo
Albacore - range 930 miles, speed 161 mph, guns 1 x 7.7mm (offensive), 1 or 2 x 7.7mm (defensive), 1 x 1,670 lb torpedo
Skua Mk II - range 760 miles, speed 225 mph, guns 4 x 7.7mm (offensive), 1 x 7.7mm (defensive), 1 x 500 lb AP bomb
SU-2 - range 685 miles, speed 300 mph, guns 4 x 7.62mm (offensive), 2 x 7.62mm (defensive), 1,320 lbs of bombs.
Fairy Battle - range 1,000 miles, speed 257 mph, guns 1 x 7.7mm (offensive), 1 x 7.7mm (defensive), 1,000 lbs of bombs
If you compare the SBD with it's contemporary single engined bombers, it's not the top in all categories (the SU 2 and TBF are faster, theoretically, and the B5N has longer range) but near the top in all of them. Plus armor, ruggedness / heavy construction, dive bombing ability and relatively heavy offensive armament make it stand out.
Naval war was a combination of attrition and Strategic warfare. Carrier duels could be decisive with Capital ships sinking in one day, meaning victory or defeat for the fleet. Here is where accuracy matters. For naval combat there were basically just two types of ship killers - dive bombers and torpedo bombers. Level bombers were essentially useless so that leaves out most of the planes above. Whereas maybe 1 out of 10 sorties from a D3A or SBD might get a hit, and perhaps 1 out of 6 from a B5N, with the torpedo hits also doing much more damage, for a level-bomber the rate of success was more like 1 out of 100. Additionally, in part because of problems with US torpedoes, in the early years of the war US Torpedo bombers were all but useless so they are pretty much out of the running too.
So this leaves the D3A, B5N, SBD, Swordfish and Ju 87 as the top (potential) naval bombers of the war.
Next factor is range - the Ju 87 never operated from carriers and had a limited range of 311 miles. That puts it out of the running even in any
theoretical carrier duel. Swordfish were used and with success but their range was a very limited 522 miles. The Albacore is a bit better on range at 930 miles but still painfully slow and defenseless. In a carrier duel against the Japanese ala Midway or Coral Sea the Royal Navy would be in serious trouble on the basis of range alone, not even taking into consideration their vulnerability issues. For that matter torpedo bombers were statistically just more vulnerable than dive bombers. Dive bombers seemed to be harder to hit by flak, than the low and slow-flying torpedo carriers, and their high maneuverability and structural strength meant that they could maneuver well against fighters.
So we are left with the D3A, B5N and SBD as the best carrier bombers in the world in 1941 or 1942. All three have good range, good bomb load, but the SBD manages this with armor, self sealing fuel tanks, and a pair of .50 cal machine guns. The B5N in particular was very vulnerable to destruction as a big, slow torpedo carrier.
And carrier duels were not always decisive on the first encounter. It turned out that a steady pressure was
also important to maintain. Even in a carrier duel, it might take several strikes before the outcome was decided, and here is where I think the SBD really stood out. The Japanese naval bombers, D3A and B5N in the beginning of the war, were excellent in terms of range and lethality, but
bad in terms of survivability. In two days of action
in the Solomons for example (24-25 Aug 1942) the IJN lost 70 aircraft, including almost all of their bombers, while damaging the CV Enterprise, whereas the US lost 20 (mostly fighters) and sunk the CVL
Ryūjō. In a single strike on Aug 24 the Japanese lost 24 out of 37 aircraft. By comparison the US Navy lost 6 out of 31 Dauntlesses that attacked
without fighter escort (due to the long range) when they sunk the
Ryūjō. This emphasizes an important fact:
The SBD had a remarkably low loss rate for an active bomber.
Carriers didn't always duel each other of course, they were also needed to attack land bases - taking islands was a major point of Pacific naval warfare after all. The SBD could be used in this way - (as could the TBF which was less helpful in Carrier vs. Carrier action) but the Japanese naval bombers were basically too fragile. In theory you could try to use something like a Swordish, Skua, or Fairey Battle this way but I would predict prohibitive casualties. This emphasizes both survivabiliy and versatility.
SBD's were also useful for scouting, ASW and sea rescue (the spotting part obviously not for picking up crews). They could be (and were) used for tactical CAS as well as Operational and Strategic Naval strikes. It was even useful in air to air combat. It was in a disadvantage against a Zero but was more than a match for a D3A or B5N, or say E-13 or F1M scout planes... with it's heavier guns, armor and self sealing tanks. Even against Zeros they sometimes scored kills (see
Swede Vejtasa).
Finally in general serviceability and maintenance issues, the SBD excelled. It was highly
available, even in the wretched conditions on Henderson Field. The best aircraft in the world is useless if it is a "hangar queen".
So
TL : DR I would say the humble SBD
was unusual. To fly 1,000 miles with a 1,000 lb bomb load and armed with heavy machine guns, armor and self sealing tanks - even if you could only manage 250 mph,
and make it back again, was a rare trait especially for a naval / carrier bomber. As a true dive bomber it had accuracy an order of magnitude better than almost all other types of bombers except torpedo carriers, and it was far more survivable than the latter which meant it could be counted on to deliver more strikes. If you could manage 10 strikes with 10% accuracy that is better than 3 strikes with 15% accuracy.
So yeah, I think it stood out due to it's intrinsic qualities. I would argue that if for example the Royal Navy had large numbers of SBD's (I know I know - production difficulties would have made that very hard to achieve) the Bismarck would have been sunk much more quickly and maybe before it wacked the Hood!
I'll argue the points about the Yak-1 and Il2 some other time, this was long enough already.