I've actually completed everything in my "completed", "on-hold", and "dropped" lists.  Shows that I really dropped or didn't watch at all are put in "not interested".  The reason I do this is that I like to keep separate sections to quickly see which were my favorites.  I watch mainly for the romance aspect, so my sections are based on that as follows:

• Completed: The main leads had good/great chemistry, the relationship was developed well, and I liked the entire series as a whole, including the storylines and secondary couples/characters.
• On-hold: The main leads had good chemistry, but only the start, first half, or parts of the series were good, and other parts started to drag because I just didn't like the storylines.  There are also some shows that were really good overall (e.g., Go Back Couple), but I didn't put them in "completed" because the main focus wasn't romance.
• Dropped: There was very little or no focus on romance, or the main leads had bad chemistry.  In some of these shows, I felt the main leads had the potential for good chemistry, but the screenwriting/producing failed to develop it well.