The reason you can't compare their powerlevels cause the way they're expressed is different. For example, if the weather here is 7 Celcius, and at yours its 44 Fahrenheit, doesn't mean that its hotter at yours cause the number is higher.
Goku has FINITE power, and his whole character is about becoming stronger than his opponents while Superman basically has infinite power, as long as theres a sun.
Other than that, there are so many series, manga and comicbooks, tons of spinoffs. You can't get a reliable source of information, because in every comicbook/manga/serie the writer just does whatever he wants.
Really, the whole debate is dumb. You can't possibly compare 2 heroes from totally different UNIVERSES.
Also, you consider yourself a DBZ-fanboy, and that already makes your conclusion biased.
