Having not played Uncharted 2 when it came out, or even in 2010 (or 2011)  for that matter, I decided to play Uncharted 2 and 3 back to back so I could easily see the differences between the two games and decide which one is better. I have noticed a lot of people, including the Giant Bomb crew, have stated they felt Uncharted 3 was great, but really just more of what they had played in Uncharted 2. After just finishing up 3, I have to say I think this opinion is very far from the truth, and here is why.
 
The Graphics: Yes, Uncharted 2 is a two year old game, but the improvement in the graphics and textures from 2-3 is a much bigger advancement than 1-2. Uncharted 2 looks good, but definitely shows its age, much more than i was expecting it to. Uncharted 3 looks as close to a pc game as I have seen a console game look. 
 
The Story: Perhaps the best improvement, The story in Uncharted 3 is by far the best in the series. Besides the love triangle, Uncharted 2 felt like Uncharted 1's plot all over again. An extremely generic power hungry villain, after a mystical artifact that of course has terrible repercussions. Uncharted 3 brought in a villain that had personality and had a connection to Drake and Sully. You get to learn some awesome information about how Drake and Sully met, Drake's past, and the game gives all the characters a much more original feel. The story had a lot more feeling to it and made me care about what was going to happen next much more than in 2. 
 
The Action: Maybe its just because Uncharted 2 did some things no other game had done before, but I came out of that game extremely disappointed in the lack of "wow" moments it had. Don't get me wrong, 2 did have its moments, but 3 was by far more impressive. The opening fight scene felt really dynamic, it flowed really well, and the animations of Drake grabbing objects and pushing guys out windows was really cool. The fire part was also awesome, along with the boat part. Naughty Dog did a lot of amazing things in the environment that I could honestly say I had never seen before in any other game.  Climbing inside a boat that is side ways, blowing a boat up with a rocket launcher, riding on horse back after cars, escaping a burning building and hanging out the back of an airplane all stood out much more to me than anything in 2 did.
 
The Originality: Uncharted 3 had a few solid moments that the first two games did not have at all. It opens up with an awesome fist fight scene, you get to play a climbing based flashback of Drake's past, the hallucination scenes were interesting, and you spend about 15 minutes just walking in the desert. These all added to the gameplay variety and to the story and each time I thought it was really cool. Also, in most cases it was something I had not seen before in any other game.  
 
The Sully Factor: One of my biggest complaints about Uncharted 2 was the lack of Sully! Honestly why did Naughty Dog decide to remove him from 80% of the game? He is such a central part of the series and is such a great character. It was so nice to see him be in the majority of 3. Also, the fact that the story centered around Drake and Sully's relationship was also really cool.
 
I came out of Uncharted 2 having enjoyed the game, but feeling disappointed and mislead by it being a GOTY winner. Uncharted 3 was the game that really made me say "thats fucking awesome" as I was playing it. I am quite surprised Giant Bomb, particularly Ryan and Brad, threw it out of their GOTY top 10 so easily by saying it was just more of what Uncharted 2 had already done. That is really not the case at all. Uncharted 3 is the superior game in a lot of ways. It does many things Uncharted 2 did not do and actually made me want them to make a fourth game. Maybe its just because people haven't played Uncharted 2 in 2 years that they can't see how different these two games are in terms of what Naughty Dog was able to accomplish.