Okay, so I haven't read a lot of Potter fic in... well... years. Honestly, I found the end of the series so lackluster that I lost interest to a large extent. But I do browse around on ao3, and an author that I have a lot of respect for bookmarked a Potter series that sounded vaguely interesting.
And it's awesome. It's more canon-centered, but it's entirely composed of 'what-if' AUs that don't extend much beyond the timeline of the books, so it's basically genfic. That's incredibly well-written and tells compelling stories
boy with a scar, by dirgewithoutmusic
I read all of them except for the unfinished one, and every single one is a gem. If I had to pick a standout, it would either be no place like home (where Harry is raised at Hogwarts) or the family evans (where Petunia actually bothers to parent Harry). But read all of them, seriously. They reminded me that as disappointing as I found the end of the series, JKR really did do a great job with worldbuilding.