didn't realize seven deadly sins was that popular. I kind of lost interest while watching the anime.
and great to know.
The yearly combined manga chart should not be used by itself as a popularity marker because those are the combined sales throughout a year for that series. The reason why Seven Deadly Sins is so high is because the TV anime started in October last year, which started boosting the manga sales significantly, including back issues. Whenever this happens for a manga, the more volumes available at that point, the higher the sales jump will be for that year. Actual popularity of a series should be judged by the total sales a new volume can attain over time, because that would be an indication of how many active readers there are still buying the series as it is released.
The trick is to also look at individual volume sales for the year: http://www.oricon.co.jp/special/48458/5/
As you can see there, One Piece can still easily sell over 3 million per volume, while Attack on Titan has hit the 2 million per volume range. Naruto is >1 million, while Tokyo Ghoul, Haikyu, and Assassination Classroom are ~1 million series. Ao Haru Ride and Silver Spoon are >900k series, and Seven Deadly Sin is behind those at ~900k. One Punch Man is a >700k series, but it's still growing in popularity, so if the anime gives it a good boost, it could climb to a ~1 million series. We'll see.