Are games giving too little in story to Players?

While I play games myself, I learn from them. And one of the things I get to experience is that in some games, after I finish the story, chances are that I don't won't have enough interest to replay it(unless it haves a variety of options like Mass Effect). But if it has multiplayer, I get into it instead of the Story Mode.

And it's not just me, it's a load of players. They say that the game didn't give them too much experience or that "The story was great, but I don't feel like playing it again". So while I was designing my game, and trying to balance the Difficulty of a game, I thought "Why not give the ability to change his experience in the game to the player?" 

Maybe I wasn't too clear on the question but let me try to explain it: Most of the players buy a game to play the Campaign (or Story Mode).  Once they finish it, they feel that they got little for what they spent on, so they rush to multiplayer if it has it. If it doesn't, then he will not play it for some time. This is assuming he already finished it in the hardest difficulty, though. Most players want a challenge, and pump the difficulty up to the hardest setting.

But after they finish it, they would want more, or DLC, or anything to enhance their experience in the game. But what happens after he finishes it? He's stuck again and won't bother playing the story again, or DLC.

But I have an experiment that I have yet to test. Which is giving the ability to change his experience in the game. How? Different Classes with different stories and Camera Models.

In a game I'm designing, the Player will be able to choose a Class, and depending the class AND difficulty, the story and the AI's Natural Behavior changes. The story will not be the same if he chooses to be an Archer in the Easy Difficulty as if he chose to be Arcer in the Hardest Difficulty. The Camera Model will stay the same,  but the story and the AI's behavior will change. The enemies will have newer attacks by each difficulty, and meet new enemies with unique characteristics and Abilities. 

Also, all of the stories are related to the main story. While I want the player's suspense to increase, I came up with the idea that the player experiences the main story first, then after he finishes, simply give him those options. To experience new stories and new in-game experience. This was while I was adjusting the Absolute difficulty of the game.

Thoughts?