Uncharted 2 is plain tedious, but the 2500 kills is much easier to do legit, surprisingly the pistol is the best gun in the game to use.
Uncharted 3 like others have said is harder, but also at the same time fun. You can get away with doing everything legit except the treasures, which is an AWFUL luck grind. But the wins come with time, expect to spend a lot of time on them if you want all the trophies. I did it back in 2013 so I'm not sure if the grenade ball game mode is still in there, but if it is, that's a good starter to get the grenade trophies. The statue co-op trophy is very hard and takes a lot of practice.
But boy are they both MEATY 100%s to have.