Oddly, despite my numerous anxieties over how good (or lousy) a writer I am, I don't tend to compare myself to other writers or think, "I wish I could write like that!!" (I might think, "I wish I could be AS FAMOUS or AS POPULAR as that," but I never wish I could write like someone else.) Maybe this is because I want my writing to be liked on its own merits, not because it sounds like someone else? I can't even compare myself to another writer, not only because I haven't the gall to do so, but because I don't really read enough fiction, especially in my genre, to say.
Maybe you need to try to take the approach I take. Instead of wanting to write like someone else, want to write like YOU write. You are the only person, after all, who has your own voice. If you were to write like one of the authors you named then you'd sound like them, and that's hardly original. It's not that authentic unless your voice is similar to theirs from the start.
Now, wanting to write AS WELL AS them, that's another story. Practice and more reading (and yes, more frustration) is the only possible solution. But even if you do end up writing as well as somebody published, it might not matter, because the readers might not find it. I think I write well, and people have told me I do, but without any way to really get my work "out there" and noticed by as many people who read published authors, I'll never know if I'm truly that good.
Think of it this way. Somewhere in this world there may be the world's greatest artist. His work has the ability to awe people, to make them laugh or cry, to make them truly think, to change their lives. Thing is, he lives in the middle of nowhere, has no social relationships, and no real contact with the rest of the world. So even if his art is the greatest in the world, nobody will know. Even if he does get his work noticed, there's no guarantee the world at large will see it. A lot depends on chance (or a good agent, or whatever).
Instead of getting frustrated, maybe you can challenge yourself to try to write as well as the people you're reading? It gives you something to aim for. But you shouldn't try to emulate them too much, because you might lose your own voice. The people you're reading were probably so successful because they didn't emulate somebody else. They were true to their own voices. (Though not having read them, I can't say for sure.)
I feel like I still haven't made my point. :/ I guess it's hard to relate when one hasn't been in the exact same situation. I know all about feeling inferior, though.
Here's one more thing to think about. You say you agonize over making a plot or a character as compelling as someone else's. Maybe you already have, it's just that it's not as compelling IN THE SAME WAY. Whether a character is compelling or not is largely a matter of opinion, after all. This "Ender's Game," for example, doesn't really sound like something I myself would care for, but that obviously doesn't mean it isn't compelling. I was going to say, maybe like me you just need to find the right readers, but you already have people clamoring for more of your work, so doesn't that tell you you've done something compelling?
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