Were you on Twitter in the weeks before the game released? They did tons of promotion. It's not billboards on 280, but that's not how advertising is in the App Store world.
As far as the game experience, it's far from being in the best of its genre (and I know many game designers who agree on that point). People like it because it's artsy and lends itself nicely to casual play, which is fine. But whatever, that's besides the point- which is that it's far from a one man indie success.
If you're specifically looking for something that fits this thread's constraint of visually stunning, one-man indie dev Escher-style puzzle game, I feel an obligation to point you at Antichamber [0].
It's got some of Echochrome's starkness to it, but with some very nice writing/dialog(?) bits that play off the game's puzzles well. Most people will find something delightful about it, though be ready for a slower paced, introspective game. It knows you know it's a puzzle game, and will punish you for it :)
(I should note that Antichamber seems to have been in development before Echochrome or Fez, and as such likely deserves the originality that has been showered on it.)
I was super excited about Fez because I loved the art style. But after twenty minutes of playing, I gave up, totally disoriented. I have a terrible sense of direction in general and that game was just me wandering around lost and miserable. :(
For me it was the first puzzle. The mechanics weren't clear and I had several glitches. The rest of the game was alright, but quite overhyped. I liked The Floor is Jelly a lot more, but it didn't get as much attention. Sometimes it pays to be a drama queen.
You can't reasonably make the claim that Fez became popular because Fish was a drama queen! It got excellent reviews and won many awards and contests. Personally, I think the attention was warranted.
I was probably not completely fair. But I really don't think Fez would've gotten the attention it got without Fish, and a bug ridden game like Fez makes me question the reviews. The gap between press reviews and user reviews on Metacritic seems to confirm my point.
Well, as a long-time gamer who loves these sorts of toy-box games, I'd say it's one of the very best. So THERE! :)
For more modest success by an actual one-man developer, you can look at Michael Brough's games. I think he makes a living off of them now, even though they're very niche.
As far as the game experience, it's far from being in the best of its genre (and I know many game designers who agree on that point). People like it because it's artsy and lends itself nicely to casual play, which is fine. But whatever, that's besides the point- which is that it's far from a one man indie success.