I had a really bad Candy Crush addiction for a while, but after getting a new phone and lost all the progress, I've never played it again.
F2P games are... how do I put this? Not horrible, but not good either. Basically, if you play for free you get screwed out of all the good stuff. There's a F2P game called Clash of Clans and it's fun, but when people who pay raids your base, you can't really fight theirs since they pay to have better stuff. I would be okay with it if it was actually free, but then no one would put care into their games because they won't get money for it.