When I was younger I used to buy plenty of games and play them for a short while, unless they grabbed my attention then I would normally finish them. Now, I'm picky on what I buy as my money is spread out to bills, kids, gas for cars, etc., Having said that, if it's a game I know I will play a lot of and get my rupees worth then I'll buy it and not look back. Anything else I'll either rent or borrow from a smuck, I mean friend, whom has bought the game already.
When I was a kid I hardly finished many games unless it was an RPG, Action platform or FPS, in my adult life not many RPG's are that great to me and can't seem to force myself to finish, most platform games are still interesting and FPS has grown much since 20 some years ago.