Personally, I think the first Uncharted is still the best of the series. A bit short maybe, but fun from start to finish, and doesn't overstay its welcome. Taps into that need for a little Indiana Jones flavor once in awhile, and does it damn well.
Only played a little of Phantom Hourglass, but from what I recall, it's pretty fun. I haven't been in any rush to pick it up for myself though, mostly because the touch controls often seemed a bit twitchy and unnecessary.