I've played most of the RAGS games available through the Collective. A few were compelling: enough story to be interesting, good enough art to create anticipation, and hard enough to be fun. RAGs is limiting because Windows, but not too much. I play in a VM. HTML5 would be oh so much more, er, accessible.
For adventure-category games, the puzzle is the thing, and that's pretty hard to do well, it seems. OTOH, a straight adaptation of any of the high-ranking text adventures in
http://www.ifcomp.org/ might yield something that's not terribly costly to produce, fun to play, and thus a worthwhile investment. I'd pay a few bucks to play an IF game with MCC-level artwork (especially if the puzzles required actually LOOKING at the art).