So ultimately, after all of that rigorous scientific enquiry and seven years of research, those plucky young scientists at the University of Leicester have come to the radical conclusion that Superman is the best/most powerful/awesomest superhero out there.
Their reasoning being that Supes, amongst other things, appears to be the most efficient solar panel in the universe with the ability to store 3.86 x 1010 J of energy every second. This would convert into each "Super Flare" released by him containing the equivalent of multiple atomic bombs.
Now, this doesn't sound as impressive as, for example, Black Bolt's planet-obliterating powers. But, when combined with his many other powers, including increased muscle density and the ability to reverse the polarity of the Earth's spin, his powers far outstrip his weaknesses, and Superman ends up at the top of the pile.
They go into a breathless amount of detail as to exactly why and how Supes is just, well, super. You can peruse it at your leisure via the links below.