+Both Anime deal with games, gambling and/or high stakes wagers.
+Both are intense/suspenseful where the players life is on the line.
+Both have "strategic mastermind" type MC's/Protagonists/Antagonists (more-so NGNL imo as Dorei-ku has only just started...).
-NGNL is more of a Suspense/Comedy/Fantasy genre, Whereas Dorei-ku is more of a Suspense/Thriller/Drama type so far it seems.
-NGNL's MC's are MUCH more enigmatic/charismatic imo and is likely a far better anime overall. Though they are similar in some aspects, the overall "feel" for Dorei-ku is darker and goes in a different direction.
I've yet to see what Dorei-ku is made of (as it's so early on in the season), but it seems to be entertaining enough thus far and I'm looking forward to seeing where it takes things! Hopefully it'll illuminate humanities darker, depraved, sadistic side without losing an entertaining, intelligent storyline. c:
*P.S. NGNL just so happens to be one of my all time FAVE anime's so I hold it in very high regard. Not many come close to it in comparison imo! 'xD - :P