Strategies to picking research projects

Just the other night I submitted the final copy of Kinodynamic RRT*: Optimal Path Planning for Systems with Linear Differential Constraints to ICRA 2013. Doing so inspired several ideas for extending the work. Of course they run the gamut -- some interesting, most not. But then how do you tell what is a potential interesting research idea versus what isn't?

I spoke to my advisor about a couple of these ideas. Curiously he was more interested in the one that I thought was the least interesting of the two. This has made me really focus on the question of what makes a good research idea. I realize that he has more experience than I so it's not a surprise that we disagreed. But to become a good researcher one needs some ability to determine what makes an idea interesting, right?

I also realize that this is not an original question and I'm certain that a quick search would yield a great number of results on the topic. But I'm more interested in first hearing your thoughts on the topic. So, if you would, please tell me how you decide whether an idea is worth pursuing?