What is a power ballad?

[byebyepride.livejournal.com]

I am watching The Hits '50 Greatest Power Ballads', or at least that's what it claims to be. Now, 'Winds of Change' -- that's a power ballad. But 'Angels' (Robbie), surely that's just a ballad? The wikipedia entry suggests that Christina Aguilera's 'Beautiful' counts (that's on now) but does REM's Everybody Hurts? (just sh!te, but also just a ballad!). I hadn't thought of 'Don't Speak' as a power ballad, but it seems to fit the bill.
Perhaps I am being old-fashioned and stuck in the past by expecting a little more rock to my power ballads?
Perhaps we should have a poll, if only I knew how.