I don't know if you're familiar with the Lego series of video games. I think the first one might have been for Star Wars. I remember outright dismissing the idea as stupid, until I actually tried the trial version of one through Xbox Live. I really enjoyed it, and I think I've bought all of them except for the Lego Movie variety. They've covered Indiana Jones, Harry Potter, Pirates of The Caribbean, Lord of The Rings, Batman (the sequel for which covered all of the DC universe) and Marvel Super Heroes. Each game has a story mode, where you play through a bunch of levels, button mashing and collecting things. When you're done, you've started to unlock features that let you do more things, and eventually you can achieve the "100%" mark, where you've done everything and collected everything. I've done it a few times: With Pirates, the two Harry Potters and Batman 2. I got close with Lord of The Rings, and I'm not sure why I didn't finish. Some of them are nearly impossible (the Star Wars Clone Wars games breaks from their winning formula so badly that it isn't really even that much fun).
I don't know that hardcore gamers give two shits about these games, because they're not really challenging, and there is no online component. They're just kind of fun time wasters. Diana has hit 100% on a few of them too, and she is definitely not a gamer. My biggest issue is that they appeal to certain obsessive compulsive qualities of my personality. And I like it.
I doubt that I would ever be diagnosed with full out OCD, but it definitely shows up in selective areas of my life (none of which would contribute to me getting rich or something useful). For example, I'm obsessive compulsive about locking doors, loading the dishwasher, turning bottles in the fridge so the label faces outward, and back in the day, some kind of CD sorting scheme that I can't explain to anyone. OK, so saying that out loud does sound a little nuts. Whatever, I embrace it.
In any case, a few weeks or months ago we scored The Hobbit version of the Lego games. It uses a lot of the same stuff from the LOTR game, so the conventions are similar. I could never get into the book, and didn't see the movie, so it's all just for fun. This particular game looks like it's possible to get the 100%. I've found myself up late a couple of nights gathering treasure and red bricks to complete the game. Provided it's not overly difficult, I enjoy the process. It doesn't require much to engage in, but it's still really satisfying.
I was thinking about that need to finish something, because you can't really bottle it. There has to be some kind of intrinsic motivator behind the effort to be totally locked into finishing. I observe that Diana gets this out of quilting projects. I get it sometimes for certain software projects, but not as much as I used to since by their nature they're never really "done." I definitely had it when I was cutting video for a living. I think it's that I like having some finished product for something I work at.
Testing that theory that obsessive compulsive completion behavior is tied to intrinsic motivators would be interesting. Seems like a strange place to find joy, but there it is.