The truth is, you do have more of a choice. In fact, there are a number of other candidates out there that are not running under either of the main party lines. For example, on the Arizona ballot, we have a Green and a Libertarian option out there. These two are an option in many states, while states outside of AZ have a few others to choose from as well (see also: this, this, and this - and yes, this one is real. For more information, here's a more complete listing.). While I am not necessarily endorsing either of these two candidates, you might be interested to find that one of these individual's values more closely match your own than either B.O. or M.R. Then again, maybe they don't, but it doesn't hurt to look into it does it?
President Obama originally ran with for office advocating 'change', but staying within the bounds of the two-party system is hardly changing anything. However, electing someone from a minority party would really shake things up, now wouldn't it? If you, like me, are tired of the same broken system of the top two always being the top two, perhaps you should consider voting to elect someone from another group.
"Isn't that throwing away my vote?"
You may be thinking voting for a smaller, lesser known candidate may be wasting your time, effort, and voice. If you use that logic to decide on a Republican or Democrat, then perhaps you are right, but consider what would happen if everyone voted for who matched their beliefs/opinions: the current system would break down to a more diverse set of options. People in the far-right, far-left, and those from the center would all rise up in popularity, while the mainstream parties would waver. Perhaps, one or another may actually win a few electoral votes!
Unfortunately, I do not have any real statistics to tell you who would be at the top of the list. There are some groups out there who have compiled data (Americans Elect, now effectively defunct, and ISideWith to name a few) showing that not everyone really agrees with either Mr. Obama or with Mr. Romney. I suggest taking the quiz at ISideWith, but this should not be your deciding factor on who you vote for! Then again, using this as a guide is probably better than blindly voting for your party's candidate simply because they represent your party (whether or not that party even represents you is a different point altogether).
What to do
Before you go to the polls (or mail in your ballot, as the case may be), take a closer look at what other candidates have to offer, and vote for who you think best represents your views and who you think will have the most positive effect on this country. If you really want change, then you're going to need to make it happen yourself; complacency is not the answer. Change is not going to happen on its own, and especially not if everyone thinks it's a lost cause.