Depends on the game, certainly. In MMOs it's a solid way to make the player play longer. Couldn't very well say that it adds to my enjoyment of the game, and in most cases I would actually say that it's what drives me away from the games to begin with or makes me despise the practice to some degree, though I have to wonder if my problem there is with the grinding or RNG specifically. That in mind, Fire Emblem Awakening and XCom are also things.
That in mind, I couldn't well say that it's always bad. I mean, if were just talking about loot that's one thing, but it also refers to the chance that a monster will Spohn or the chance that an enemy will do a certain attack, and in some cases I think that can be fun. I'd like a dynamic experience and that makes for a dynamic experience, so it's hard for me not to be down. Games like Dragon Age and Neverwinter Nights use this for conversation, and depending on the way you play can make the overall game more interesting depending on the outcome. So, in the sense that you can add unpredictability to what would be a static encounter, yeah, I do think it can be fun. It's all about context, really. And design philosophy. After all, in the cases where people would normally agree that is isn't fun, it probably wasn't meant to be to begin with.