It's hard to really judge this movie.
On the one hand, it did a good job keeping true to the franchise. All the Pokemon were immediately recognizable, and some of the established rules/tropes of the world were held up in the film (Police working side-by-side with Growlithe, for example).
But just about everything else about it was just...bad. The pace was off in the beginning, jumping from one scene to the next in an obvious effort to get to the Pikachu introduction quicker. The acting was godawful, as was the writing. Ryan Reynolds' quick one liners can't rescue the bland performances by the lead human characters.
Overall, I'd love for them to try again. But for an actual Pokemon movie. None of the detective stuff. Just a coming of age tale of a new trainer picking his partner and exploring the Pokemon world.