Death Parade (A-) This is one of the smaller % of anime that DIDN'T start as a manga. As mentioned, it's the spiritual successor to Death Note. I don't think it needs a second season because doing these bar games a second time takes the novelty away from the series. This and No Game No Life would be the two series I'd recommend for those new to anime and want to take in a single short season (12-episode) series.
Assassination Classroom (B+) I can see why some, especially those who like more violence in their shounen given the title of the series, might not like this one. It wouldn't be surprising if the person who created this story was a former educator, or had educators in his family. There's a lot of profundities about teaching and life in general here. It's a also a nice commentary on the student-teacher relationship and the Japanese school system (which I may do some teaching at in 2020). It got better in the second season and really good as it went along towards the end, IMO. First season a B, second a B+. Ending an A-. So B+ it is for the series.
FLCL (B) This one also didn't start as a manga. "When the three powerhouse creators of Eden of the East, Gurren Lagann and Neon Genesis Evangelion bumped heads, they spawned the series that broke all the rules - then broke the mold." Oh boy. So much has been said about this one and I was excited to watch it. I actually ordered the Bluray from Amazon. It's the subject of much debate about what this somewhat ambiguous story is actually about, although puberty, sexuality, and growing up are three generally agreed-upon themes. There's surely a lot to explore in these short 6 episodes, but FLCL is so loud, obnoxious and offputtng that I don't care to examine this story any further - a story I didn't find too interesting in the first place. I won't be watching the new series.