Completion Percentage, when is enough enough?

I've played a lot of games, but my completion percentage is fairly low.

I have a philosophy when playing video games. To not be afraid to move on, I feel like this is antithetical to this website but I do like how it encourages me to at least try and get a bit more out of my games.

I wanted to ask what you're guys opinions are. Personally, when I've beat the story or beat the final boss I feel that I have beaten the game and that it's time to move on. If I love the game I might try and get some more out of it, maybe beat some optional bosses or extra stages but I don't feel that i have to get every achievement.

Similarly if I'm -not- enjoying a game I feel that I should just move on and play something better, but it's on this point that I'm kind of sticking. For example I played Zombie Army 4 the other day and found it to be, not my thing. I beat 2 levels and I feel like I'm done, but the completion percentage is so low. 11%

My question is, what would you do in this situation? Complete the story anyway despite not really liking it? Do I complete another level in a hope to push that percentage up to something more respectable? Should I just -not- play games I'm not completely into any more to avoid this happening in the future? Or should I just forget about it? It's not that important.

As someone who's been on a crusade to get through their backlog for the past 2+ years, I'm determined to get my money's worth out of my games. I'm also a completionist, so I've made myself suffer through completing some games I haven't liked as well. I know that's probably not a popular opinion as most people I know who like achievements/trophies will absolutely drop a game if they don't like it (my one friend, in particular, tells me that he's fine with playing a game for a couple hours and dropping it forever if he feels like he got his $5, or whatever he paid during some sale, worth). I think it depends on what you want out of anything. How much do you care about achievements? Do you care about completions and your percentages as much or not? Does you care about all of that as much as having fun? Do you often regret spending more time on a game you aren't having fun with? Those are all questions only you can answer.