Mass Effect all the way, although it should be Mass Effect 1. Also prefer Fallout 3 to Skyrim, but that's a personal preference. Skyrim is arguably the better game, I just prefer post apocalyptic sci fi to fantasy. I think Skyrim will benefit a lot from only having been released a year ago, so it will unfortunately probably be a Skyrim v Portal final. Still a good battle.
Why is Portal so acclaimed though? I mean, it was a great game, but the immense praise it gets is verging on ridiculous. It was fun for a few hours and it was pretty impressive how simple yet gripping it was, but it's not like it was the gaming experience of a life time, like I felt with the Mass Effect trilogy.