1950s: Raleigh Sports. From 1900 to 1946, the USA market had been largely closed to foreign brands, as a result of prohibitive import duties that had been put in place to help the American bicycle industry recover from the implosion of the very late 1890s. Relaxation of duties started in the post World War II era, first with British, in an attempt to help them rebuild their cycle industry, to aid in repayment of their war debt to the. USA. American armed forces stationed in England during the war had become familiar with British IGH models, so when Raleigh aggressively expanded in the opened USA market in the 1950s, their Sports model became a best seller and icon of the era.
1960s: Schwinn Sting-Ray. You say you what a revolution? The Sting-Ray was the genesis of the hi-riser craze that swept the children's market for about a decade, eventually giving rise to the BMX market. It could even be argued that Staing-Ray and its brethen drove the rise of the 10 speed, because once they had grown out of their hi-risers, the baby boomer teens wanted something "new", with some of the excitement they experienced with the Mustang. They certainly weren't going to settle for their parents' single speed roadsters.
1970s. Masi Gran Ctiterium. I'll always associate the 1970s with the early 1970s bicycle boom and the rise of the derailleur equipped lightweight bicycle to mass acceptance. From that perspective, my choice would be the Peugeot UO8, as it was arguably the most successful model for the first couple of boom years. Then the American public realized the Japanese were masters of QC and value, so the market started shifting. However, the OP"s requirement is Italian and the most respected Italian builders of the boom era were Cinelli, Colnago and Masi. I'm giving the edge to Masi because it more of a pop culture icon due to being Dave's bicycle in Breaking Away.
1980s: Specialized Stumpjumper. To me, the legacy of the of the 1980s is the rise of the ATB and the symbol of that is the Specialized Stumpjumper. ATBs almost killed off the road bicycle in the late 1980s. If the ATB hadn't come along, the bicycle industry would probably have been ina pretty sorry state by 1990. SBI's Stumpjumper was the first of the mass volume ATBs and the best seller that spawned a new discipline.
For those with a 1980s road bicycle bent, I'd say a 1987 Centurion Ironman Expert. In the 1980s the mid-range sports bicycle became the most popular adult class and Japan was where it was at. Almost without exception, the Japanese manufacture mid-range models were well manufactured and provided excellent value but the Centurion was set apart by it's Dave Scott endorsement and Ironman license. The fuschia and yellow paint epitomized the pastel coloured Miami Vice influenced colour trends of the mid to late 1980s.
1990s: I'm not sure which one, because I don't think there was a standout. But it would be a Taiwanese manufactured hybrid.
Now, none of these would necessarily be by personal choices but for the average person, these would probably be bicycles that symbolized their era and the evolution of the bicycle industry.
Edit: I had originally typed Schwinn Mustang, cross breeding my American and Canadian hi-risers.
