Update as of [v.21022] Having played and finished all the previous games from NLT, From LE to ToN to TGO and now SoTS, I think my favourite would actually be Treasure of Nadia. It's really unfortunate to say this, but there really hasn't been much improvements to the newer games, infact, some aspects of the game has been going downhill. One of the most important thing about these games is the characters, and the designed of the girls here are pretty ugly. ToN has some of the best girls in Clare, Jessica, Diana & Sofia, while the other girls in the game are all decent as well. Now in SoTS, the design of the girls are straight up ugly.. with the only notable ones being Cleopatra, Anya, Lola and Grace. Heck, even the side characters Lucy and Nora are better than majority of the main girls. There is also no buildup in terms of relationship development between the characters, and many of them just straight up goes to sex. In terms of scenes and animations, ToN was one of the better VNs at the time of release, you'd expect improvements to them with the newer games like TGO and SoTS, but not much improvements has been made since, which is a disappointment. Story is also a little messy, you get no background information into the virusthat is happening, and just jump into it. Can't really recommended playing this game, unfortunately.
Pros:
-One of the more likeable MC between all 4 games
-Story has been a little better than TGO so far
-Pretty good puzzles so far
-VO is alright
Cons:
-Transitions in cutscenes is pretty bad
-No improvements in terms of animations and graphics since ToN, and feels really outdated now
-Poor design of the main cast
-Poor character development
-Lack of background information to the virus
-Combat is interesting, but poorly executed
-Side girls are not really needed, just there to waste money for mindless scenes
-Mindless loop in circling around places for things
-Very linear gameplay