Less "Bang, Zoom!" More "Weep, Whimper"
To the Moon is at its worst when it's trying to be a video game.
Part of this is down to the RPG Maker engine powering it: the point-and-click controls feel awkward when they work correctly, to say nothing of how irritatingly broken they become when the pathfinding falls apart; using keys to simulate a gamepad is more reliable, but hardly convenient; contextual actions and their hitboxes malfunction regularly. And some problems are really only attributable to the game's design: like the frequently lazy and tedious maps, and the universally boring puzzles.
That being said, gameplay is not what makes To the Moon noteworthy -- it's the writing. The game's plot, although slow to build at first, is genuinely interesting and unique (despite some superficial similarities to Eternal Sunshine of the Spotless Mind). And the way that this story is told through dialog is generally pretty great. To the Moon's writing is markedly better than the vast majority of craptastic video game stories, and arguably approaches the quality level of critically-acclaimed films.
It's not perfect. Comic "relief" sometimes comes at inappropriate moments, breaking dramatic tension. Some portions of the game move slow, whether due to the unwanted interruption of bad gameplay, or simply from scripted elements literally moving very slowly. And I have some minor, distributed quibbles, like the dialog's weird approach to non-profane exclamations.
To put a point on it: this isn't the best game story I've experienced. But it ranks pretty high, with some particularly sophisticated use of foreshadowing, and fairly effective ... emotion, type, stuff. Feelings and shit.
To the Moon is bad as a game, but good enough as a story to make that game worth tolerating.
Better than: Dear Esther
Not as good as: Analogue: A Hate Story (which really had a better sense of brevity)
The story is memorable: but the game's strongest message might be don't make an adventure game in RPG Maker.