There are some real whoppers in your list, and critical omissions too. I'll
concentrate on the USA, which I know best:

USA

On 2-Oct-2007, Eunometic wrote:

P-38 Had the range and performance to protect US bombers. It
prevented the German Airforce from fielding heavy aircraft firing
rockets, or impunely attacking bombers under the protection of heavy
armour.

TOTALLY WRONG. The P-38 was a FAILURE in the ETO, due to poor high altitude
performance from defective engines and unreliable turbosuperchargers. Its
unheated cockpits were another significant liability because of their effect
on pilot performance. It was a long-range wonder in the Pacific, where it
fought at lower altitudes, but was a failure in the ETO.

In parallel with this is your assertion that the P-51 was "not essential."
Only the P-51 had the necessary escort range. Without it the daylight
bombing campaign would have failed in late 1943. Moreover, the 51
outperformed virtually all-prop driven Axis fighters. This aircraft won the
air war for the Allies in the ETO.

One statistic says it all. In 1945 the only 8th AF fighter group still
flying the P-47 was the 56th FG. All others flew the 51. This wasn't an
accident. BTW, the "wet wing" P-47Ms you tout had huge engine reliability
problems, which kept them grounded most of the time.

A truly essential aircraft you overlook was the C-47 transport. "General
Dwight Eisenhower described the C-47 as one of the four machines that won
World War II, along with the bulldozer, 6x6 truck, and the landing craft."
http://www.faqs.org/docs/air/avc47.html

In the Pacific the early "essentials" were the Wildcat and the Dauntless.

JAPAN

In addition to the A6M Zero, I think you also need to include the two other
carrier aircraft Japan possessed at the outset: the "Val" dive bomber and
the "Kate" torpedo/level bomber. All three were essential to Japanese naval
air power, even after defeat at Midway.

I'm not sure any Japanese twin engine bomber was "essential." They all had
fatal design flaws (lack of armor and flammability) that made them little
more than flying targets. The Japanese air war was first won, then lost, by
their single engine aircraft.

Speaking of which, I don't see the Army Ki-84 as essential. IMHO that
plaudit goes the the Nakajima Hayabusa Ki-43, which like the Zero served
throughout the entire war.

USSR

I don't think you can exclude the Yak fighters, especially the Yak-9. I
will also include a surprising choice for an "essential" Soviet A/C: the
Bell P-39. It is remarkable how many Soviet aces not only flew that
aircraft, but greatly favored it.

My comments, FWIW.

Brian