For those that really enjoy 'early' Genesis as showcased by @Markir choice of Foxtrot, there is a rich seam of music that continues to this day in the shape of Steve Hackett's solo work.
Many people believe that Genesis changed when Gabriel left (and they did) but to me the even more profound changes came when Steve Hackett the guitarist left. Genesis made A Trick of the Tail and Wind and Wuthering with Steve but without Peter and both are fine albums in the early Genesis tradition. It was only after those albums that Phil Collins influence on the music took them down an extremely commercial but far less interesting route. So anyone that really enjoys Foxtrot will also like the albums that came before it (Trespass and Nursery Cryme) and the four that came after (Selling England by the Pound, Lamb Lies Down on Broadway, Wind and Wuthering and Trick of the Tail). I have purposely omitted the album Genesis to Exodus (their very first album). Whilst it is interesting to Geeks like me, it is unrepresentative of their later work.
Steve has been making music and touring since he left Genesis in 1977 and continues to make inspired guitar based prog rock. I can recommend for anyone interested, his debut solo album Voyage of the Acolyte as typical of his work. If you can catch him live, he tours annually and plays half his own stuff and the second half is devoted to early Genesis and frankly, his live show musically eclipses what live early Genesis could produce albeit without the bizarre red dress and foxes head that Gabriel had a penchant for. There are some wonderful full concerts on You Tube. Here is an example of his band playing Suppers Ready (with full orchestra).
A couple have mentioned Foxtrot as almost like classical music and there is a great deal of truth in that. Most of the band were educated at Charterhouse where they received a classic education and Banks mother was a classical pianist and he in particular was immersed in the genre from a very early age and has gone on to compose and record classical music. There are some wonderful examples of prog/classical compositions in their work. Check out Firth of Fifth on Selling England and Fountain of Salmacis on Nursery Cryme where the classic influence is particularly clear.