Well although I enjoyed Mass Effect 2 a lot, I would not personally consider it a GOTY contender this early. I have a hard time really talking about GOTY until later in the year as you are getting nominees from a whole. However, it's really hard for me to put that up there as a nominee even right now.
Obviously there are a lot of people who love the series, especially this second one, but I have very high expectations out of Bioware and potentially them not living up to them with the ME series is affecting this decision. But I'll get back to you on this in November haha. Depending how the rest of the games are, could be a contender. I remember last year I held on to Arkham Asylum as the GOTY until one of the last games I played of the year, Assassin's Creed II which eventually became my GOTY 2009. Could be exact opposite this year where one of the first I play turns out to be it.
