This question is based on the assumption that the Soviet forces started in a position of superiority, and over the 45 years of the Cold War slowly degraded in capabilities to the point of inferiority. I would argue that that is an incorrect assumption, and I would rather argue that the balance of power in Europe swung wildly between NATO and WP as technology, platforms, and doctrine changed.

To give an example, if we look at the balance of power right after World War Two, both forces were relatively equal. The Allies and the SU had major forces in Europe, veteran forces which were equipped with the latest in military hardware. While each force had its strengths and weaknesses, they were both very potent military forces. However, in the years following World War Two, the Soviet Union successfully preserved its combat capabilities, while Europe and the US allowed their demobilization to atrophy their current capabilities, as well as prevent a modernization of new capabilities. European forces were still equipped with American World War Two surplus, while the United States had precious few of its newest weapons. The Korean War, and specifically 1950, was the nadir of this degradation.

In the wake of NATO fears over a larger Communist invasion, Germany was rearmed, European armies were strengthened with better US surplus, and the American forces were rebuilt with cutting edge weapons able to counter the Soviet's. Further, the doctrinal stagnation of the 1940s was replaced by a reorganization which saw the incorporation of tactical nuclear weapons into offensive and defensive schemes. While the PentAtomic and ROAD divisions were still pretty large and inflexible, the represented a revival in operational and strategic thought concerning a potential war. So, by the late 1950s NATO was in a pretty good place, their equipment had improved and reached parity with the Soviets, while the WP satellite forces still had their early 50s equipment, and the Soviet's latest weapons were still on the drawing board.

I would argue that this typified the balance of power in Europe. Crises and conflict would distract NATO from the European theatre, and precisely at these times the WP would introduce new weapons and capabilities into their force. The Vietnam conflict was another such nadir for NATO capabilities in Europe. But then the inequality in forces would force NATO and the US to recommit themselves to European defense by introducing new weapons, technology, and doctrine which would do to the Soviets what the Soviets had previously done to NATO's capabilities.

This continued roughly into the 1980s. The mid 1980s were another highpoint for NATO's defense of Europe, when the Air-Land Battle concept, precision guided munitions, and the most advanced tanks yet produced countered the aging Soviet equipment. They countered by developing their own equivalents to this NATO technology, but the instability of the collapse of the Warsaw Pact and the Soviet Union understandably prevented any serious attempt at modernization that the Soviets had previously planned.

I suscribe what is explained by /u/BeondTheGrave, now, I am not sure that the West ever considered the Eastern bloc as inferior. I was in the Army during the last decade of the Cold War and we never saw the WP as inferior. We did know that part of our strategy was to compensate overwhelming numbers with quality, that said we never perceived them as inferior.

I was part of an attack helicopter unit and we had a lot of respect for their AA, especially the ZSU-23. We saw the T-72 as a very hard to knock down target and the Mil-23 as an impressive beast.

We did perceive some of the Soviet allies as inferior in terms of training and overall of dubious reliability to the Soviet cause. Our intelligence suggested that they may not have been so loyal nor have the will to sustain the war effort. In addition seems confirmed that some of the satellite countries like Romania and Bulgaria for instance had "B" material.

Luckily we never had to put all this to test.