The band Genesis went through several phases, but mainly two. In the first, with Peter Gabriel and Steve Hackett, they were definitely prog rock, lots of Mellotron, long tracks, opaque lyrics and tricksy rhythms. Then two left and they went all pop/disco.
One of the labels other groups are given is “Genesis clone”. Marillion have this, and I can’t say anything about them as I have never really listened to much of their work. Another such band is IQ.
And this is wrong and so unfair.
Of course IQ are a prog rock band (lots of long tracks, Mellotron, tricksy rhythms and opaque lyrics). There are bound to be similarities with the line up of drums/bass/guitar/keyboards/vocals. But IQ are heavier and more guitar based, for a start.
IQ began in 1981, and they are still going. They have a very loyal following.
Their first ‘proper’ album is Tales From The Lush Attic (1983). This is available on CD and was remixed relatively recently and is worth a listen.
If you ask IQ fans they will mention a few albums as the best, really top class albums.