OK normalise it for battery life then.
If you have a phone with a honking great battery that gives you 48 hours it's going to take longer than one that only holds 16 hours.
1. The graphs tell you how much endurance aka battery life you'll get out of XX minutes of charging.
2. You can pull up the maximum battery life of all these phones which confirms right away that outside of that Oppo phone, S6/S6 Edge/Note 4 beat everything in terms of balance of battery life vs. charging time.
http://www.phonearena.com/reviews/Samsung-Galaxy-S6-Review_id3965/page/4
So now, it's absolutely not necessary to normalize against battery's mAH capacity when there is enough data from looking at maximum charge time and using the charging % vs. endurance linked earlier.
For example, after 30 min of charging, you'll get 39hr out of S6, 43hr out of S6 Edge, 40hr out of Note 4 but only 22hr out of M9 quick charge and 28hr out of iPhone 6 plus (ipad charger).
Alternatively, we can use percentages. In 30 min iPhone 6 Plus charges to only 35% but S6 to 54%. The maximum battery life of the iPhone 6+ is 6hr+32min vs. 7h+14min on the S6 per the link above. So clearly the S6 charges way faster and has longer on-screen battery life to boot. GSM arena actually confirms where the S6 outperforms the iPhone 6 Plus in both Wi-Fi and Video viewing!
With % charging times, endurance, and total battery life, we can quickly and easily see which phones are most efficient/convenient for charging during the day (obviously if you mostly charge your phone overnight, then whether it charges in 3 hours or 1 hour is irrelevant).
S5 manages to beat the S6 in calling only.
Now look at the total charging time for the S5/iPhone 6/6+ - the S6 beats them easily. The iPhone 6 performs particularly poorly because it takes longer to charge when looking at 15 min, 30 min or up to 100%, but loses in battery life in all 3 categories to the S6/S6 Edge. Given that it's the primary competitor, I would say the S6 wins this battle by a mile. The S6 isn't even thicker than the iPhone 6 but has 4X as many pixels, a way faster SoC and a larger 5.1" screen, but still blows the S6 in efficiency. That's why it's hilarious how some people in this thread tried to downplay 14nm node as nothing but a marketing gimmick. Good thing A9 will be made on 14nm because right now the iPhone 6 fares poorly in 3G talk time and video viewing.
If you are an electrical engineer doing an indepth study of different battery technologies sure, but it would mean nothing to a consumer. All a consumer would care about is the ratio of how long they can use their phone vs how long they have it charging. I find the 15-30 minute charge endurance test to be very valuable, as it can indicate how screwed you might or might not be if you are about to get on a plane and only have 10 minutes to charge your phone which is at 5%. Or if you're a super heavy power user, how much charging they can get done while eating lunch or something
That's exactly it! Since some phones don't have swappable batteries, for those of us who often run into situations where we need to charge a phone in 5-15 min, it matters a great deal if we can get more battery life in this short time span. Those graphs indicate exactly that measurement. Of course for someone with a more stable charging schedule (i.e, charging at night every day or every 2 days) this is less relevant. However, it's cool to know that Quick Charging 2.0 is not just a marketing gimmick.