Man I keep thinking mass effect and assasin's creed are 2008 cus I play em on windows and that's when the windows releases were
but you guys are right, 2007 games. Wow this gets tough. Unfortunately I played ME2 before I played mass effect. I bought ME2 in like 2010, a little after it's released, loved it and picked up the first one for like $10 when I was still buying games on disc. And... well... I couldn't get into it. The combat was massively improved in ME2, at least for pc. Controls and cover system were pretty shoddy in the first one. And I really disliked having to piece together gear and the leveling system seemed too complicated for the type of game it was. So in the end I never finished it cus I just preferred to keep going back to the sequel.
There's a couple others I haven't played but feel should be mentioned. Super Mario Galaxy and Zelda Phantom Hourglass. Not sure how big the latter was, but any zelda game is usually pretty good. And even though I never played galaxy I have heard from many it's the best mario game ever. It has a 97 aggregate on metacritic, the highest for any mario game I can find. For comparison new super mario bros for wii has an 87, Mario 64 is 94, mario sunshine is 92.
Bioshocks another I didn't have time for sadly and fps isn't really my thing. I did enjoy assassin's creed but again it lacks the polish of the sequels.
Uncharted also released that year. Another series I have never played but has tempted me to buy a playstation so many times.
Civ4 BTS was easily my favorite game from 2007 but I already voted for Civ4 so not going to recast that vote for an expansion.
Thus I'm going mass effect. Even though I didn't personally find it appealing enough, the story is great and the franchise is fantastic and I have actually played it!
Here's a decent article highlighting some games from 2007.
http://www.gamespot.com/articles/why-2007-was-the-best-year-in-gaming/1100-6424367/