I own an Xbox. I also own a grand total of (I think) five games for that Xbox.
I own the first two Assassin's Creed games. The second one, at least, has more replay value than any other game I have ever played. Why? Because even after you beat the main story, you can spend hours and hours running around the various cities, climbing walls and doing flips off buildings, killing enemies in a variety of original ways. I love the main story, but I have more fun doing this than I do playing missions. The story and the characters are far from the most important part of the game to me. The aspect of the game that I like best is the aspect that I have the most control over, with the least interference from the game itself.
I also own Modern Warfare 2. Like a dutiful player, I beat the single-player campaign before moving on to the multiplayer. Here's an example of a game that doesn't even try to get me invested in a story. When you buy this game, you are buying the multiplayer experience. This is probably the worst game that I own, but I still have a lot of fun playing multiplayer. Yes, it's frustrating, and yes there are a lot of obnoxious douchebags to play against, but at the end of the day, I remember the moments where I succeeded, not where I failed. That's what Call of Duty is good at: making the player feel good about their ability. Unfortunately, this comes with a hefty price tag; the game is dumber than a bag of hammers.
And then there's my favorite game of all time: Portal 2. I can't count the number of times that I have played through this game. Dozens, likely. I know exactly where every portal goes for every single puzzle in the game. But I'm not playing through for the plot. I'm playing for the experience. I love being in that world, running through those hallways, interacting with those characters. I like thinking with portals.
My point is this: Story in games is a pointless exercise. Yes, it can be done with great success. But I believe that you should focus more on making your game fun to play than on telling a worthwhile story. A game with too much of the latter and not enough of the former is worthless as a game. "Yeah, i get that you put a lot of work into the complexities of this plot, but where's the part where I get to play the game?"