Bollocks I say. ME2 is an early front runner by the look of things, not a dark horse at all.
Demon's Souls is a classic example of a Dark horse: not even available world wide; sold a lot less than 1 million to date; hardly known at all outside PS3 circles; everyone expected Dragon Age: Origins to take out everything RPG related this year, and some overall GOTYs as well. ME2 will have none of those elements making it a dark horse contender, it's the leading RPG of 2010 from what I can see, how does that make it a dark horse?
“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.” - Bertrand Russell
"When the power of love overcomes the love of power, the world will know peace."
Jimi Hendrix