When Alan Moore took over Rob Liefeld's Supreme he remade the character into a homage to Silver Age Superman and was also using the story to comment on the current state of comics and Superman especially. He also made fun of British comic writers (guys like Neil Gaiman, Warren Ellis, Mark Millar, Grant Morrison, and Alan Moore) trying to make characters like Superman more mature and complex but only on a surface level. He also made concepts like Radar, the Hound Supreme and Suprema, his sister work a LOT better when DC brought back Krypto and original/classic Supergirl.
Plus the concept of the Supremacy a place where all reboots, alternate versions of Supreme go when they fall out of favor is still more interesting than most of the multiverse stuff that DC and Marvel do now of days.
Supreme: The Story of the Year, Supreme: The Return, and Judgement Day shows that weird out there concepts can be used to tell complex stories that deal with real world issues and history and still be extremely entertaining as wel. These are some of the BEST Superman stories not staring Superman ever told.