Presicely what it says. Name the top 10 most powerful heroes and villains of the DC Universe.
BAHAHA! Of all? Or just those lower than cosmic level. You probably won't get two lists that are the same. There are so many beings that are on reality warper, cosmic, universal or even MULTIVERSAL levels, that it's a joke to ask to just name the top 10 and be able to consider that list...in any way accurate.
Since you said heroes and villains, I'm going to presume that you are talking characters that are Justice League level.
In which case, and assuming no more than one villain per rogue gallery and only one iteration of the same character or idea I'm going with...
Superman 1 Million
White Lantern Kyle Rayner
Flash (Wally West)
With no restrictions at all?
Gold Superman Prime 1 Million
I might say Emperor Joker, but that might be cheating considering he's just Joker with Mr. Mxyzptlk's power.
The White Life Entity
And...I don't know...the Radiant.
And honestly, minimum 70% of all this is wrong. There are probably a hundred characters that should be on this list, or at least are stronger than those on this list, who just totally slipped my mind. This is almost an impossible question.