Thanks Rukaio. I'll check them out.
Out of those you mentioned, I only know of Detective Conan. Actually, I was an avid reader and follower of that series, but haven't read new chapters of it for a while due to time constraints and mostly cause of the foot-dragging plots/story. The one big thing I'm curious about right now is what exactly happened to Shuichi Akai, is he alive, is he dead? They kept introducing new mysterious characters and antagonists and like you said, only once in a blue moon, actually do a big reveal to tie things up. At this point, I think no matter how shocking or clever the ending, and reveal of the big boss is, there will be major plot holes involved.
I remembered reading a pretty good detective manga called Kindaichi Case Files. Let's see if I can find it online for a reread.
Heard a lot of good things about Fullmetal Alchemist so gotta start on that as soon as possible it seems.