Super 8 Ultra Brothers (or whatever title variation you prefer) is a great Ultraman movie. The production values are fairly good, but the strength of this movie is the script and the direction (as well as some solid acting from a lot of people reprising their roles from various Ultra TV shows). Character development is excellent for an Ultraman movie or TV show, but that actually sells this movie a bit short.
The development of the characters and the plot is done at just the right pace. It isn't rushed, nor is it too slow. And Hiroshi Nagano carries the movie well as the lead (returning to his role as Daigo Madoka from the Ultraman Tiga series). He was likable on the TV show, and he's likable here. He has a charm and charisma that carries the movie well.
And then you've got four of the original Ultramen, and they've got great chemistry together along with their female leads from their respective series. Bringing in the older actors gives this movie great nostalgia value to go along with all of it's other positive qualities.
Of course, like most Ultraman projects the effects are less than Hollywood Blockbuster quality (with the kaiju suits being particularly unrealistic, as usual), but better than most of the Ultra series and/or movies. There isn't anything here from an effects or suit standpoint that takes the viewer out of the movie - it's all solid, even if not great.
Ultimately, this is a great Ultraman movie. Very satisfying and wildly entertaining.