The story was better in Uncharted 1.
The whole treasure turning people in to monsters got me very surprised and thats what I like. I didn't get the same feeling in Uncharted 2. Also, there was very little of Sully in Uncharted 2. Another thing that I didn't like too much is that in U2, 90% of the time you have someone with you, in U1, at times you will be accompanied by someone else but not so much.
However, U2 has small boss fights like the guy on the train, the helicopter, tank etc. It also has a longer campaign and more weapons but I would still give the campaign to U1.
I agree with the multiplayer factor. I've put many many hours into it and it's one of my favs this gen.