To Finish or Not to Finish
Question: Every time I come up with an idea for a novel, I start writing and then come up with a better idea that I think has a better chance of getting me published and/or seems more fun to write. So I abandon that project and start another, only to do the same thing to that one a couple chapters in. And yet I feel like all my started novels are too similar for every one of them to get published, were I to finish them all and them to actually be that good. But how am I supposed to know which one has the most potential? I could use someone else's opinion.
Yours is quite a common problem. Writers often speak of their latest, exciting idea as the "bright and shiny." The problem is that, like a new tool, any bright and shiny idea soon becomes dull as you work with it. This usually occurs in act two or the middle portion of the book, which is always a bit of a quagmire. That doesn't mean it's a bad idea.
I'm sure you realize that becoming an author requires actually finishing a book. That means you can't abandon an idea when it becomes dull and start pursuing the next "bright and shiny" idea.
One way to get yourself through that middle is to become more of a plotter. Develop a good, reasonably detailed outline, that you can be excited about. When you get stuck in the middle, your outline should remind you where you are headed next. In fact, you don't have to write your chapters in order. If you know where the story is going, you can set aside a chapter you're stuck on and write a different part of the story, returning to the stuck place when things become more clear. Once you have a draft, revising and polishing it is much easier than writing from scratch.
Apart from that, it takes a certain - no, make that a significant - amount of discipline to finish a book. Whether you set a certain number of words or pages per day or per week, you need a schedule you can stick to without fail.
P.S. If all your story ideas are similar, you might consider taking the best ideas from all of them and creating an outline for one awesome book.