Cogenitor, no question. But if you had A Night In Sickbay on the list, I might have voted differently.
Angie, you took the word right out of my mouth. "Cute" entirely sums up Carbon Creek for me ... well, 99% of it. There was one detail about it that I was very impressed with, and that was The Kid -- specifically, "who did he turn out to be?" Within five minutes of his first appearance on screen, I was bracing myself for the inevitable post-script revelation that he went on to command the first Mars mission, or something similar, but -- it never came. (In Roddenberry's Trek, it would have been inevitable.) I didn't even bother to watch Enterprise during its first run, and the first time I saw it was a year or two ago, in reruns. This was one of the first episodes I saw, and things like that convinced me that maybe Trek had grown up a bit and Enterprise was worth a look.
Singularity ... well, Trek has certain wells that it draws water from too often for my taste. I don't have a problem with new twists on old ideas, but seems to me that "all the humans are disabled but the lone alien/android/whatever is immune and saves everyone" is an idea Trek's already done, and done, and done ...
First Flight -- fun, but ultimately didn't strike me as anything more than yet another "buddies who are also rivals" story; not that Trek's done many of those stories, but it's hardly a fresh idea. Dead Stop -- an interesting premise, and I particularly liked the fact that they knew nothing more about the repair station at the end of the show than at the beginning. Both episodes were enjoyable, nice ways to spend an hour, but neither seemed to be anything to get terribly excited about.
One of the things I like about Enterprise is that it wasn't afraid to attack some of Trek's sacred cows, and as beatified bovines go, the Prime Directive is pretty high on the list. And it doesn't take very much scrutiny to reveal that it's far from a perfect policy, to put it mildly. Even though the principle isn't formally known as the PD yet, Enterprise put it under a microscope for a very unflattering view in two episodes. Dear Doctor went for a more arid, intellectual and subtle examination of it, whereas Cogenitor was brutally "in your face," and both were refreshingly free of the self-congratulatory smugness that some other PD-centered Trek has had.