I have three examples.
1. Demon's Souls : This was one of my first PS3 games, and I didn't really know what to expect. I knew the game was supposed to be hard and unforgiving, which is fine, but the whole feel of the game didn't click for me. Combat and movement felt heavy, and I didn't really like the first level after the tutorial (especially the boss, which seemed pretty lame and uninspired). I stopped playing and decided to give it another shot after a few months. And I don't know how it happened but I was instantly hooked. Suddenly the mechanics were perfect, the enemies and bosses were awesome and the challenge didn't let me stop playing. It was the biggest gaming addiction of my adult life, which would be surpassed only by the sequel.
2. Assassin's Creed II : I started playing this in October 2011 while dogsitting for a week in my girlfriend's house. The main thing on my mind was Dark Souls, which I had preordered and was anxiously waiting its delivery. It was probably my most anticipated game ever, and gaming-wise I couldn't really think about anything else. It was like I wasn't mentally available for any other game. Nevertheless I played ACII, completing something like two thirds of the storyline. It was fun, sure, but eventually I grew pretty tired of it. And of course, Dark Souls arrived shortly afterwards and completely shattered any chance of continuing ACII. I picked it up again after seeing (and loving) videos and reviews of ACIII, and it was awesome. I completed the storyline, bought AC:Brotherhood and completed it in a few days. I will get ACIII as soon as I can get a good deal on it.
3. I haven't given it a second chance yet, but am seriously considering it : Dead Space. I played it for about an hour (probably a bit less) and didn't like what I saw. The beginning was very slow and the map was confusing. Most of the hour was spent running around the same areas, looking for some switch or valve or something. I don't usually judge a game by its opening hours but this one really turned me off. So badly that I even sold the game on eBay. I am considering re-buying this when it goes on sale on Steam for a ridiculous price.
How about yours?