I finished Mass Effect 2 a few nights ago. Overall, I really enjoyed it. It is better than the first one in almost everyday. My total playtime was around 40 hours I believe. I probably spent more time mining planets than I wanted.
Even though I clocked in over 40 hours, I felt like the main storyline was pretty brief and not as satisfying as the first game. Looking back, you spend about 70% of the game recruiting your team and earning their "loyalty". By the time your team is fully assembled and you take on the main quest, it is over in a heartbeat, and I found that disheartening.
The game's climax also wasn't as impressive as the first one's, in my opinion, although it was still plenty exciting. I managed to finish the game without losing any teammates, since apparently you can lose multiple mates. In fact, you can lose your entire time and even Shepard bites the dust if you make certain decisions, leaving Joker the sole survivor. I find that very interesting and wonder how that will play our for the 3rd game.
I did enjoy the final mission, as you really have to assume command and make plenty of decisions about what to do and which teammates to send to do certain tasks. I take it that this plays heavily into determining who survives, since choosing badly and sending someone not "qualified" for a certain job probably results in them not making it. This is all just speculation on my point though. Bottom line, that final missions was pretty cool and I wish there were more missions like that, where your entire team is involved. I actually hope that all of ME3's main quest missions use a variation of this, since it makes more sense than 3 individuals going off and doing everything while the others are hanging out on the Normandy.
I want to do another playthrough, importing my new ME2 character, but I'm worried how that will affect my ME3 import. I want to make sure all the decisions I made in this first playthrough are the ones to carry over to ME3, but I want to mess around in my 2nd playthrough and make some drastically different decisions to see how they play out. Not sure how that will work.
Anyway, fantastic game. I'd say early runner for GotY but it is only February, much to early to even be mentioning that.
Speaking of which, I've yet to name my GotY for 2009 . . .