Certain aspects were better, yes. That's because the Soviets made different trade-offs in the design -- variously because of doctrine, time constraints, availability of exotic materials (and the ability to use them in manufacturing), and "helpful" direction from Moscow.
The MiG-25 "Foxbat" is a famous example. To succeed in it's role as an high-speed interceptor it should have been made from titanium. But it's a very expensive and difficult metal to work with, so temperature critical parts were instead made from stainless steel. In the west there were lots of jokes about it rusting in the rain and the use of vacuum tubes, but tubes allowed it to have a very powerful radar. Plus that's what they had to work with (the Soviets having great difficulties making high-current semiconductors).
I don’t know if that is true or not, but if so, I guess it is a stirring endorsement of the idea of being a nice liberal democracy that people want to move to.
There was single significant defection before the introduction of the "teen" fighters, codenamed HAVE DOUGHNUT, and even it was not actually Soviet (an Iraqi pilot defected to Israel). All the other defections (which there were several) happened using old/non-fighter aircraft (iirc there were several MiG-15/17/19 which were essentially Korean War era designs), or happened after the teens were designed.
He might be talking about Belenko's defection with a MIG-25 to Hokkaido in the early 1970s. Though neither aircraft is really related to the other except in very basic visual sensibilities (twin engine, twin tail).
And F-15 had its first flight four years before the MiG-25 defection. So unless they had time machine at hand its unlikely that it had major influence on F-15 design
My impression is the Westerners’ best guess about the Mig-25 contributed significantly to the design of the F-15 and helped to make it what it is. Getting their hands on it was a relief, or even a let down.
The alternative scenario, where the Mig-25 really was generations ahead, plays out in the movie Firefox from 1982 where the US is so far behind they have to steal a Soviet Mig-31 superplane. Good for laugh today, but once upon a time…
The rumor I heard is Soviet intelligence infiltrated American industry and stole what they thought were plans for America’s next generation air superiority fighter. What they’d obtained were the plans for Plymouth’s Roadrunner Superbird, thus the Mig-25’s uncanny resemblance. Proof: https://robbreport.com/motors/cars/1970-plymouth-superbird-a...
The, probably slightly played up, version I heard is that the US saw the propaganda version of the Mig-25, and so built the F-15 to counter that imaginary beast.
I'd be curious to know which aircraft were actually better than their US contemporaries and by which criteria they'd be judged better.
The Mig-25 seems like a good example of a Soviet aircraft considered better than its US contemporaries, at the time. Misunderstanding and misinformation let the US to think they were far, far behind the Soviet Union. Viktor Belenko cleared that up! It was a plane good at just one thing, with downsides that would never let it through a (non-CIA-directed) US procurement process. On the plus side, competition, fear, and rivalry, drove the US to some amazing research, engineering, and innovation.
As a child at a local military airshow, the F-15 was awesome, dangerously beautiful. Shamed even the X-wings and Tie fighters I'd just seen on the big screen. Many years later, I had a similar feeling watching an Su-27 at Farnborough; Sukhoi captured some aesthetic that Mikoyan-Gurevich never seemed to get right, and did it better than any western contemporary.
I don't think it's controversial to say that MiG-21 compared favorably to its contemporaries when introduced. Afaik it successfully fought off newer, much more expensive, American F-4s in Vietnam war.
The MiG-25 "Foxbat" is a famous example. To succeed in it's role as an high-speed interceptor it should have been made from titanium. But it's a very expensive and difficult metal to work with, so temperature critical parts were instead made from stainless steel. In the west there were lots of jokes about it rusting in the rain and the use of vacuum tubes, but tubes allowed it to have a very powerful radar. Plus that's what they had to work with (the Soviets having great difficulties making high-current semiconductors).