The movie Yamamoto made a reasonable point. The combat aircraft on carriers were of three main types: fighters, dive bombers, and torpedo bombers. Comparing the Japanese and US planes of each type:

Fighters: The Japanese Mitsubishi A6M Zero (Zeke) and US Grumman F4F Wildcat both went into service in 1940. The Zero was revolutionary, packing superb performance and good armament into a lightweight airframe (allowing a relatively poor engine to provide that superb performance). The Zero came as a rude shock to the Allies when they first encountered it in combat; their fighters in the Asian-Pacific theatre at the start of the Pacific War were generally greatly outclassed by it. The Wildcat was an improvement over those early fighters, but the Zero still outperformed the Wildcat in agility and climb rate, and enormously in range. The Wildcat was a much tougher plane, with self-sealing fuel tanks and armour protecting the pilot (the Zero, to achieve its light weight, sacrificed such things). With skilled pilots using tactics that reduced the effect of the Zero's superior agility, the Wildcat could, and did, hold its own against the Zero. The next generation of USN fighters - the Hellcat and Corsair - would in the future overwhelm the Zero, but they were yet to come. The Wildcat was not terrible in comparison to the Zero, but the Japanese had seen little effective use of fighters by the US. First, most US fighters they had encountered had been inferior, compared to the Wildcat. Second, experienced Japanese pilots had fought green US pilots. The famed Wildcat tactic for coping with the Zero's agility, the "Thach weave", developed by USN pilot John Thach, only made its combat debut in the Battle of Midway. The predecessor of the Wildcat, the Brewster F2A Buffalo was also flown in the battle, by Marine fighter squadron VMF-221 based on Midway.

Dive bombers: The USN dive bomber, the Douglas SBD Dauntless, was a good aircraft: long range, maneuverable, and a respectable bomb load. However, the Japanese Aichi D3A (Val) was better in many ways: faster, longer ranged, more maneuverable (the Dauntless carried a somewhat heavier bomb load). Again, Japanese experience was generally with experienced Japanese pilots being compared with green USN pilots.

Torpedo bombers: While the Wildcat was outperformed in many ways by the Zero, its good armament and toughness made it a respectable opponent. "Terrible" is not accurate. Similarly, while the Val outperformed the Dauntless in many ways, the Dauntless was still a good aircraft, and, again, "terrible" is not accurate. However, when it comes to torpedo bombers, the Japanese Nakajima B5N (Kate) outperformed the USN Douglas TBD Devastator so thoroughly - almost double the speed, cruise speed, and rate of climb, and also longer ranged - that "terrible" is a quite accurate comparison. Even the Devastator's much-improved successor, the Grumman TBF Avenger, didn't match the performance of the Kate. (Six Avengers took part in the battle, flying from Midway. Flying unescorted, 5 were shot down, and the 6th damaged.)

The movie Yamamoto's "terrible" is a fair comment based on past experience. However, that experience was based mostly on different fighters, and green US pilots. The Battle of Midway would prove him wrong, with US fighters and dive bombers proving their worth - if they were really terrible, they wouldn't have sunk 4 Japanese carriers. (The Devastators, on the other hand, sank none. Only 6 survived of the 41 taking part in the battle. None hit targets with their torpedoes.)