Top Best Series Enders
City of Glass (The Mortal Instruments #3) by Cassandra Clare [for me, the series felt like it should have ended here]
Top Worst Series Enders
I know there are a couple series out there that either I read and didn't mind the ending (AKA, Bloodrose by Andrea Cremer) or I haven't read them yet (AKA, Requiem by Lauren Oliver). But I'm glad to have read more series that ended best rather than worst.