[Switchblade]

My favorite, as I'll always say to anyone who'll listen, is Max. But in regards to your categories:

Best story: I've fallen a bit behind on it, but I'd still probably say Orb. It has a really good story that centers around a really engaging main character. I think Nexus tried really hard, but it had a tendency to get stuck up its own ass sometimes, especially when it came to the main character's girlfriend.

Best characters: Max, hands down. Every Ultra series has its core cast of the main hero and his support team, but of all the shows I've seen so far, Max did the best job of making them all feel really well developed and likable.

Production values: Ginga. I really liked how everything was based around one abandoned high school and... nah, just kidding. Ginga seemingly had one of the lowest budgets of any modern tokusatsu series. This is a harder one to judge since the newer shows are obviously going to look better than the older ones, but I think for sheer quality of design in terms of sets, special effects, monsters, etc. I'd probably have to say Gaia. That was a really well put together series that looks incredibly damn good for the late 90s.