Gromuhl: I think the term "adventure" is too generic to label a single genre. The full genre title of games like money island is "point 'n click adventure". These games are basically puzzle games with added narrative. Adventures like outcast are very rare. As Outcast wasn't a huge success back then (unfortunately) there was not much follow up. The sequel was canned before release and that's the end of it. What I see though, is that some rpg's become more and more like outcast. In contrast to dry stats, you get a more streamlined adventure. You give these examples yourself: The Elder Scrolls, Fallout 3/New Vegas. (You might even put Just Cause (2) and GTA4 under the same umbrella, but I personally think they are a bit too arcade). The fusion of many genres cause some games to become more like the Outcast that you and I like if you look at it this way. It's true that many things are simplified, but many games start to give us hardcore modes that remove all the extra help (like the recent Deus Ex), games like Dark Souls even take it to extremes. If you take a closer look at the indie games market, there is even more! I don't think a genre is lost. I think there is more adventure to be had than ever.
I disagree that major RPGs like Fallout3 and Skyrim count as "adventure" games. That blurs the line between "adventure" and "rpg" too much for me. This might just be me but the dynamics of those types of games, most notably the (essentially) turn-based combat of Fallout made me lose immersion and no longer feel as though it were an "adventure".
Deus Ex, sure, but there are too few games like it (and it and its kin have some serious consolitis these days). I've been getting my fix from games like the modern Tomb Raider games, though they put platforming above "adventuring". Not sure if I'd call games like that "adventure" games, but they're closer than most IMO.
I do wish we had more games like this, preferably games that aren't constrained in playability today by their decrepit tech that was hailed as being advanced in years past (eg:Outcast).