I really liked the supernatural elements of UC1 and UC2, not too over the top but the little bits really made the games more than just an action game. I know some people of course hated the supernatural stuff and prefer the more realistic versions in UC4.
On the other hand I absolutely love the pirate theme of UC4, its one of my favorite eras and I would easily pay $20-40/mo if ND would put out a 3-4 hour story DLC every month.
Really tough for me, especially since I only finished the UCC recently (first time) and UC4 last week so they are all still fresh in my mind. Right now I'd put it as
UC2 > UC4 (by a HAIR) > UC3 > UC1
Mostly due to the combat, I thought crushing in UC1 was really difficult whereas it felt easier in UC2 and UC3, and back to really hard in UC4 (except if you turned on cheats).
Story wise honestly I love em all and I think without UC1-3 UC4's story makes no sense, but on the other hand I am not a huge fan of the retconning of Sam in UC4, especially as it seems to diminish Scully and Nate's story.
Damn, the entire topic just makes me sad that it may be years before we get more Uncharted
We need more publishers dipping into this Tomb Raider / Uncharted segment.