What makes a time travel story good isn't the machine or lack thereof, it's the consistency. A good time travel story sets up its rules for time travel, sticks to them, and makes a good plot out of it. This is what makes the story pass the "suspension of disbelief" test--not the believability of the machine or devices involved, but whether the story has a self-consistent set of rules and abides by it. Of course, it isn't a coincidence that the stories that don't try to fit hard science into the mix are the same ones that tend to violate their own rules.
A simple example of this being violated is the case of having a story that tries to use both the "many worlds" theory of time travel and the "paradox" theory of time travel. Obviously, they're mutually incompatible. Another common example is the concept of "San Dimas Time"--having a "race against the clock" situation in a time travel story, even though this makes absolutely no sense at all. To quote TVTropes:
"As a result, events in two different time periods are shown to happen concurrently, so that people two years in the past may only have X minutes to stop the villain from committing some terrible act in the present, even though they should technically have X minutes plus two years to sort it all out. This, of course, makes no sense at all."
The best time travel film I've seen recently is Primer. The story is quite convoluted--enjoy your multiple temporal paradoxes and the fact that most of the timelines are merely implied to exist, not shown--but it is still quite a good watch. And for when you're done, there are charts on the internet explaining the full extent of all the events involved, so you can figure out those last few loose ends for yourself.
You would think Mallett would have gotten the scant few hundred thou he needs to test his circulating ring laser by now. I think I first heard of him and his hypothesis in 2001.
A simple example of this being violated is the case of having a story that tries to use both the "many worlds" theory of time travel and the "paradox" theory of time travel. Obviously, they're mutually incompatible. Another common example is the concept of "San Dimas Time"--having a "race against the clock" situation in a time travel story, even though this makes absolutely no sense at all. To quote TVTropes:
"As a result, events in two different time periods are shown to happen concurrently, so that people two years in the past may only have X minutes to stop the villain from committing some terrible act in the present, even though they should technically have X minutes plus two years to sort it all out. This, of course, makes no sense at all."
The best time travel film I've seen recently is Primer. The story is quite convoluted--enjoy your multiple temporal paradoxes and the fact that most of the timelines are merely implied to exist, not shown--but it is still quite a good watch. And for when you're done, there are charts on the internet explaining the full extent of all the events involved, so you can figure out those last few loose ends for yourself.