all i have so far is my main characters(2) and a princess gets taken by a dark lord. please help me

That's pretty vague. Why not have those three main characters being kidnapped, then have another hero quest to resque them, and then once he frees them, have the hero get taken instead? That way, the three former prisoners have to rescue the hero.

That's all I got.

How about the dark lord doesn't have experience in kidnapping and his army is a mess.

how would he be ranked 'dark lord' if he didn't have experience for a kidnapping or forming troops?

I say make whatever, just not a princess being kidnapped. Mario brothers are there for that.

You Could make the story about the Dark Lord and the Hero, two seperate story arcs, the Dark lord taking Princess(s) to help this bigger plan and the Hero that is hired by a Kingdom to protect their princess and start the story from there.

I suggest taking mental reflection time and really pondering on what you want your story to be, maybe a little more innovative?

Ton of games have the dark lord, princess, etc.

How about having the Princess being the orchestator of her kidnapping, and the Dark lord is merely a pawn, or is working for her. Have a ransom, to be payed for the safe return of the princes, by the king. Then the princess uses these funds to finance her coupe. Her reason will be that she will never ascend to power due to her being the youngest of three siblings. So she orchestrates the death of her family line, all the while returning miracously unharmed by the hero, who doesn't know she's plotted all this.

For a twist you could have the Dark Lord turn out to be the Hero, with his own ambition to rule the kingdom.

That's a start I guess.

I like that, either that or the dark princess orchestrated her own kidnapping b/c she needs the money so that she can elope with the dark lord.

Or maybe the hero orchestrates his own kidnapping as Geath Ruze described and the princess has to go rescue him because she is a badass princess, well-trained in the arts of figting - not really a damsel in distress-type.

It's already been said once, but I'll say it again. Think about what YOU want to happen in your story. As an example, I'm wanting to make a game called Slayers' Reign.

When coming up with ideas for it, I had to know what sort of things I wanted to see first. For starters, I like dragons a whole lot, and so I decided to have dragons be a large focus in the game. Not only that, but I wanted that during at least some of the game, the dragons would be playable. And of course, I wanted the hero to have some sort of relationship with the dragons (a relationship could be good or really really bad). I wanted a character that hated dragons so much, he wanted nothing more than to see their extinction.

But wait, I needed to find a reason why this guy hates dragons so much. Obviously, coming up with ideas is easy. It's giving them detail that's hard. So I had to come up with some possible reasons. Did the guy's village get burnt down by a fire-breathing dragon? Did a dragon kill his sister? Or maybe he came across a scene of a really serious crime, and a dragon was found to be at the wrong place at the wrong time, thus the person thought the dragon did whatever it was. In the end, I decided that the guy caught a dragon leading an army of monsters into his world in an attempt for world domination. Of course, once more, I had to figure out why the dragons wanted control over the world, but I won't say what the reason was.

Does this give you an idea of what to do? Just start out by jotting down things you'd like to happen. You've got a start by having a Princess get kidnapped by a Dark Lord. Try to flesh it out a bit more, or put down a few other ideas that you'd want to happen, such as the hero discovering that the Dark Lord is actually working for somewhere else. Once you've got a bunch of ideas, you'll be able to piece things together a bit better. Some things you might not be able to work in, and you'll still have to try to give more detail to those ideas, but it'll be a lot more to go on than what you have now.

I hope that helps, and isn't too confusing. I sometimes don't have a great way with words when explaining things.

My story is really generic, but it has plently of humour and side quests. Here's a summary of it that might provide inspiration:

The greatest warrior/sorcerer in the world has turned to evil in a greedy attempt for power. He releases many monsters to fight for his army to conquer the small kingdoms of the land. The king of the kingdom of Perthon forges and alliance with 2 other nations, but the land must unite completly to survive the onslaught. So the king sends his nephew with 3 companions to unite the land and kill the dark lord.
Along the way the hero unites a couple kingdoms, kills a witch, frees a dragon infested town, fights gladiators, loses companions, gains companions and can even find a secret kingdom, an evil hippy camp and an impossibly difficult dungeon maze. And I'm not even done yet.

If you don't have the dedication to build a story, then how are you going to have perseverence for building the game? I agree with Dray and Fay, come up with something that flips your switches-not ours.