Soviets and Chinese lost more MiG-15’s during the Korean War than Americans lost F-86’s. By 1970’s things were relatively even. MiG-29 first flew in 1977, not long after the end of the Vietnam War. It was a good aircraft at the time. It may have outperformed older F/A-18’s (A & B). Most F/A-18’s currently in Navy service are Super Hornets (E & F), which are newer, more powerful, and have stealth capabilities, though they are not as stealthy as F-22 and F-35.
During 1980’s, Soviet military tech was already getting stagnant. Domestic computer industry was primitive (suffice to say that, by the end of the 80’s, most Soviet computers were IBM 360 ripoffs), the whole system was mired in bureaucracy. 90’s were a lost decade. They’ve been trying to turn things around recently, but it’s hard.