This was taken from another message board that I was on but I believe it gives you an accurate portrayal of both Superman and Captain Marvel. They are said to be virtual equals in the powers department.
17) In Kingdom Come, Superman was assaulted by Captain Marvel with lightning. Many see this as Captain Marvel almost killing Superman., as well as evidence of Supermans extreme vulnerability to magic. An unbiased look at this event reveals otherwise. First of all, the lightning emanates from Shazam, one of the higher cosmic powers in the DCU. It is Marvels very power source and in fact conveys the power of Zeus, another higher power in the DCU. As an example of its power, Billy used it to crack open the Gulag in Kingdom Come. Said Gulag was designed by Scott Free, master escape artist, and constructed using New Genesis technology, which in past issues has been used to travel into the suns core. In addition the Gulag was constructed to contain literally hundreds of powerful and dangerous metahumans. Marvel busted open this Gulag with his magic lightning.
Superman withstood at least four (that we saw) of these bolts with the power of ZEUS. He likely withstood a lot more than 4 because it is implied that Marvel was reigning lightning down on Superman off-panel the whole time that the story cuts away to Batman and Wonder Womans exchange. Such an assault would have easily killed virtually anyone else in the DCU. Far from being dead, however, Superman required only a couple of seconds pause to gather his wits, used his own superspeed to match the speed of Mercury, and pull Marvel back into the lightning. (And thus win the fight, a often overlooked fact). A battering like that and still he could match the speed of Mercury. From there on, although obviously bloodied, Superman appears fairly intact. In fact, he is still conscious (actually far from out of it), talking comfortably and coherently as he erases the years of brainwashing from Billy, and doesnt even have the gravelly, uneven word bubbles used to signify serious injuries in comics. He also survives the nuclear explosion, albeit from hundreds of feet away, yet it was still sufficient to kill almost every other metahuman not protected by the Green Lantern.
Just one minor correction, Solomon was actually a Hebrew king from the Old Testament.