Genesis isn't even a band that you should use compilations to get into anyway IMO. Listen to Selling England and Invisible Touch. You get a taste of the two major eras and you'll know where to go from there.
IMO, you should start from
Trespass and move onward. Hearing their prog roots in the Gabriel-era shines light on their music as it evolved into pop-rock, with that tinge of prog you hear in tracks like "Fading Lights" and "Driving Home The Last Spike", or most of
Duke. They changed, but it was an evolution and not a sudden change, unlike bands like Yes or even King Crimson, both of which had drastic line-up changes that affected the band's sound. Genesis lost members, tweaks sounds, and each album was slightly different than the last, but moving forward to something new.
There can be fans of IT and WCD who probably skip the longer songs and only like the hit singles, and there can be fans of SEBTP and ATOTT that love the proggy, complex stuff the most, but to truly understand the band and their journey, the beginning-to-end is the way to go. At least, from
Trespass to
We Can't Dance.
-Marc.