I watched all three seasons which I loved but so far I'm not a big fan of the 4th season. I'm wondering if there is another drama like this. That has a different story each episode and deals with the main plot during the first and the last episodes.
Thanks...
Totally agree with you about the 4th season, and particularly the first few episodes, it's not the same as it was with the brilliant first 3 seasons (it's one writer for season 1-3, then two other writers for season 4).

Other series that I'd recommend with different stories each episode, are Vampire Prosecutor (1 and 2), and the Japanese drama Mr Brain.
I'm already planning to watch vampire prospector and I have already seen Mr Brain. 
i started watching bad guys and so far it looks interesting.
if god's quiz continued with the same format as season 1&2 I think it could have lasted longer. 
I watched the Japanese show Aidou (the episodes that have eng sub) and it's really close to what I want. 
Too many shows are using the only main storyline the entire drama. Which I got tired of thanks to American tv shows.
Special Affairs Team Ten is a great procedural drama!
You could try Dr. Frost. Great analysing during each cases and little bit of action. And each episode concentrate on different cases except first and couple last episodes that brings the plot together.
I would also recommend Missing Noir M. It deals with different case in each episode (there are some exceptions) and it's really good :)
The cases are really elaborated and how the main character solves them together with his partner is interesting.

Also similar are: Vampire Detective, Pied Piper and even though I haven't seen it yet, I guess Police Unit 38 is also similiar since it's an OCN drama.
--> OCN makes great dramas, almost every drama that was recommended to you is an OCN drama
I've been told that "Ten" and "missing noir m" isn't that good. 
I second Dr.Frost. was a very good show that I followed up after Liar Game
Ten season 1 is good. Solid gold. Ten season 2 has a weird ending though.
if you like medical drama, try Doctor X (japanese) its episodal but also has a main plot going on