What turned me from casual Genesis fan to huge Genesis fan was the 1981 release of "Abacab". And while Top 40 radio stations were playing "No Reply At All", album rock stations from DC101 and 3WV to the original XL102, started rolling the album's title track, a six-plus minute musical extravaganza that singlehandedly raised my level of interest in a band that would become one of my all-time favorites.
That status continued to be solidified with their next two releases, "Genesis" in 1983 and "Invisible Touch" a few years later.
This is undoubtedly one of the top jams in this musical journey. If you've never heard it, take seven minutes out of your lunch break, or throw this one on the laptop when you get home, and transport yourself back to a much simpler time. :)