Uncharted 1 is a fine game. It feels a little "generic" in that it lacks gigantic setpieces of its sequels i.e. it isn't trying its hardest to be a movie, but the writing, characters, and sense of adventure are all there.
Uncharted 2 ramped things up. The pacing is fantastic as ND knew when to fire on all cylinders and when to let the player breathe (conversely, the engines don't stop in U3). I'd say that it takes everything that was done well in the first game and elevates it--the setpieces are very, very well done and still feel a little grounded (obviously nothing in this game is realistic, but the natural progression of the story/events never feels super contrived like that of U3). The story gets more complex as you understand the characters better. HOW MANY MEN HAVE YOU KILLED? It's nothing introspective or extremely deep, but ND added more dimension to the cast in this one. Also, this game features the train level aka one of the most stunning things visually and every faux michael bay game dev's wet dream. Crazy climax.
Uncharted 3 is a fun popcorn palette cleanser. It doesn't reach for anything meaningful and it throws away any chance of that by lacking guts (peep the Sully arc). The setpieces are damn good and memorable, but they come too often and almost beat the player over the head. THE MANSION IS BURNING. THE BOAT IS SINKING. THE PLANE IS CRASHING. It's a blast to play but amidst all of the craziness you lose a GOAL and feel like you're being carried from one big event to the next. Which is fine if that's what you are there for.
All three share common problems like not being the best shooters and containing plenty of low risk climbing sequences that get a little tedious (U2 comments on this a lot having drake say stuff like "oh god not more of this" etc and I find that funny) and having weird mythological third acts that never deliver like the earlier stages of each game. So if you find something intrinsicly wrong with the way one of the games plays, you're going to disagree with it in the rest of the trilogy too. However, I'd still suggest giving Uncharted 2 a shot as imo it is the most meaningful of the three and it's undoubtedly a landmark title of last generation. If anything, you can make your own opinion on it.