Genesis is one of the bands that really led me to get into high-end audio. I saw them twice (And Then There Were Three and Abacab) and Gabriel solo twice (Three and So). Previous comments about how they changed after Gabriel left are all true and some of the later stuff is far more commercially oriented. That said, writing good pop tunes is very hard to do consistently and the pop stuff they did was all done to a superior level.
Favorites, for me like many others, are hard to pick. I enjoyed all of the stuff with Gabriel and have multiple copies on domestic, English and Japanese pressings. the later stuff is highlighted by Trick of the Tail and both double live sets. Abacab also represents a fusion that worked well for me.
Happy listening to it all!