I still say the most overrated was the P-47. Very average rate of climb, poor maneuverability and certainly not enough range when introduced. In combat by April 1943 with no provision for drop tanks until August and then relegated to ground attack by January '44 when command decided all P-51s should go to the 8th AF and all P-47s should be transferred to the 9th AF (tactical). And yet over 15000 produced.
Let's not forget the 56th FG chose to keep their P-47s once the P-51 entered service with the Eighth, which highlights one thing about the P-47, its pilots liked it. A quick look at Wiki (yes, I know...) shows why the P-47 was not overrated.
"Luftwaffe ace Heinz Bär said that the P-47 "could absorb an astounding amount of lead [from shooting at it] and had to be handled very carefully".
When your enemy says this about you, you have their respect.
"Although the North American P-51 Mustang replaced the P-47 in the long-range escort role in Europe, the Thunderbolt still ended the war with 3,752 air-to-air kills claimed in over 746,000 sorties of all types, at the cost of 3,499 P-47s to all causes in combat."
"The P-47 gradually became the USAAF's primary fighter-bomber, by late 1943, early versions of the P-47D carrying 500 lb (230 kg) bombs underneath their bellies, mid-production versions of the P-47D could carry 1,000 lb (450 kg) bombs and M8 4.5 in (115 mm) rockets under their wings or from the last version of the P-47D in 1944, 5 in (130 mm) High-velocity aircraft rockets (HVARs, also known as "Holy Moses"). From D-Day until VE day, Thunderbolt pilots claimed to have destroyed 86,000 railroad cars, 9,000 locomotives, 6,000 armored fighting vehicles, and 68,000 trucks. During Operation Cobra, in the vicinity of Roncey, P-47 Thunderbolts of the 405th Fighter group destroyed a German column of 122 tanks, 259 other vehicles, and 11 artillery pieces."
Impressive stats. Says a lot about the utilization of the aircraft, which shows that it certainly wasn't overrated at the time.