Twinfalls said:
...instances of which the developers themselves may not have specifically foreseen.
So Oblivion is the most emergent game ever
.
Seriously though, emergence is very subjective. What is clear from the rules or unforseeable depends on the insight of the observer/designer.
As for Deus Ex, I'd say that there probably were some cases of emergent behaviour (or lack of developer foresight).
For example:
Using the explosive enemies to blow lockers open without needing your own explosive.
Climbing buildings using two proximity mines (standing on one, picking up and replacing the other...).
Those aren't amazingly impressive, and the second isn't desirable. However, they are emergent in the sense that they arise from a combination of factors, and weren't intentionally designed that way.
I'd have thought the first is fairly obvious, and the second amounts to saying: wow - there are bugs in our game we didn't anticipate. (Apparently, the developers knew about neither).
I certainly agree that Deus Ex isn't a good example of emergence though. Every "emergent" factor I know of in Deus Ex has a pretty local influence, and could be predicted easily enough. [there's nothing really different between the above examples, and pushing around + jumping on and off of crates. All are predictable, but "emergent" - the crates situation is just that much more obvious.]
It did have a few small non-linear aspects. E.g. whether Paul lives or dies, whether the Doctor fellow follows you. Both of these have minor medium term consequences. Better than nothing, but not worth much celebration. [Paul living or dying doesn't really add much though, since either the player will presume that he has to die (thinking that there is no choice), or he'll choose to stick around and help so that he survives. It can add replay value if you didn't save him the first time, but doesn't do anything for the first playthrough].
I wouldn't really call the three endings non-linear, since the game doesn't go on from that point. It's nice to be able to decide how things end, but there are no branches, since the game is over.