Look at the list of the highest rated games of 2010. See how many times Mass Effect 2 and its expansions shows up. I count 3 with a score of 85 or better. The game of Mass Effect 2 itself is the top scoring of the year with a 94, which makes it tied for 3rd place with a bunch of games as one of the best PC games of all time.
Sorry, got a little excited there for a second. It's a great game, with RPG elements and FPS elements that does a better job than Fallout in my opinion and has a *much* better story too. It's like Final Fantasy story and FMV meets Star Wars mythology meets RPG inventory and upgrades meets FPS combat with the unique twist of pause-and-plan combat and the best use of cover I've seen, and a pretty good balance as far as how much damage you can give/take before dying (unlike the ridiculous amount of damage enemies can take in Borderlands) and realistic feeling accuracy spread of weapons. The weapons and upgrades are good too but I have to say I preferred the inventory of the first Mass Effect, other than how you had to manage hundreds of ammo upgrades and such. I've looked for a comparable game now that I'm done with Mass Effect and halfway through Mass Effect 2 but nothing compares with all of the same elements.
A bonus is that the dialog choices and storyline options you made in Mass Effect get transferred to Mass Effect 2 by importing your savegame, and will also continue into Mass Effect 3. That's just amazing in my opinion. It's the way games should be made. I could keep going but you get the picture. I put the game up there in the same league as the Zelda series, which says a lot.