I think WoW is a terrible game, but thats only because the things it does well are things I don't really enjoy in my games, and the parts I would enjoy it does poorly. But I know other people do enjoy those things, and I can see it does them fairly well (better than most competitors, at least), so the only thing I really have against it is it means more of my friends are playing that together instead of games, with me, that I actually enjoy. But most popular doesn't always equal the best, though. There might be better games than WoW in that market (I don't know, of course) but its hard to compete when switching over would mean leaving all youve earned and everyone you know behind, just because its a better game. Most people I know don't play WoW because its their favorite game - they play so they can play a game with their friends. Its universality, its mainstream nature, that is its real advantage, more than its quality.
Of course, universality is very much something dwarf fortress doesn't have much of. Its very much a niche game, but there's a place for it there, and Toady is happy with it there, so I'll keep my complaints within the boundary of "What issues about the game turn me off, aside from it being the type of game it is." Most people I know are turned off because its just not their type of game. Most of the rest, honestly - the graphics. But what turns me off about DF? One of the problems I do have with it is one of the same problems I have with WoW - its a horrible time sink, a lot of which involves things happening that don't require you to actually play, but do you require you to be present. The low FPS doesn't help that problem, but isn't the main issue - announcements that pause are.
Hopefully, with the ability to turn off pause announcements in the next version, that major gripe will be addressed. Once work quotas and standing orders are added in, I don't think it will be a problem.
Other than that - lack of difficulty in things that should be hard (fighting off sieges, farming) and great difficulty in things that should be easy (trying to figure out the menus, building a flute of a given material, installing a graphics pack).
I can use the ASCII, but I don't like it, and its a much bigger turn off for other people. Some packaged tilesets and a way to switch between them (especially in game) would be greatly appreciated.
So what turns me off about the game the most? The fact that its not finished yet.