I've seen this tag floating around for a while and been thinking of my own answers each time I see it, so here's mine :)
1. A Popular Book or series that you didn't like.
The Fifth Wave series by Rick Yancey.
I. Do. Not.Get.It. I thought this book was one of the stupidest things I have ever read.
2. A Popular Book or series that every one else seems to hate but you love.
Fallen Series by Lauren Kate.
Personally, I really liked this series. It wasn't the most spectacular writing or anything. I came in rather late on the fallen angel YA trope, this series was the first of that kind I read and love it. Yet most of the reviewers I follow and bloggers who's blogs I adore, seem to detest this series. I didn't think it was that bad.
3. A Love Triangle where the main character ended up with the person you did NOT want them to end up with.
This is a hard one for me to answer as I've not actually finished that many series and most of the ones I have I've been pretty satisfied with the conclusion. The only thing that comes to mind was I never impressed with the Ron/Hermione thing at the end of Harry Potter. Didn't sit well with me really.
4. A popular book Genre that you hardly reach for.
Steampunk. I've read a few things in the Steampunk genre but it is not really one that holds any interest to me. With the exception of the Lotus War trilogy, everything else I've read in this genre I've found very meh.
5. A popular or beloved character that you do not like.
As mentioned also in SlowReader's Kingdom's Unpopular Opinion post, she pretty much hit the nail on the head for this answer. My own is pretty much the same. Do not get the fangirling over Rowan from Heir of Fire. Don't get it at all. Rowan didn't particularly do anything for me. I can understand the character development in the series, and what he was there for, but just...meh. As much as I loved the Mortal Instruments, Jace pretty much pissed me off from start to finish.
6. A popular author that you can't seem to get into.
Colleen Hoover. Her books just don't interest me. At all.
Anything by John Green. The man's arrogance and general poor attitude has put me off reading any of his books at all.
7. A popular book trope that you're tired of seeing.
Chosen One Special Snowflakes who are ordinary and boring and not pretty, when they're more special and prettier than everyone. Special Snowflake heroines with red or auburn hair. Dead or absentee mothers.
8. A popular series that you have no interest in reading.
The DUFF books. Just don't interest me.
9.The saying goes "The book is always better than the movie", but what movie or T.V. show adaptation do you prefer more than the book?
Lord of the Rings Trilogy. I have tried twice to read this book. I had it on my currently reading list for two years and barely got into it. I watch the movies over and over, but just can't seem to get into the book.