I really liked 2. Exploring Columbia for the first time is similar to exploring Rapture for the first time (though I preferred Rapture) which is something 2 can't/doesn't do. Don't expect that a return to Rapture will be the same as exploring it again for the first time, and I think you would enjoy 2 just fine. It is all new parts of Rapture, however, and it's 10 years later, so there are differences. 2 Definitely has highlights as well, that outshine portions of the Irrational games.

If it's a choice betwixt playing 1 again and playing 2, I would recommend playing 2.

In fact, (and I realize I might get run out of town on a sky-rail for saying this) I think the combat/gameplay was best in 2.

So there.