FEZ may very well be a masterpiece.
The attention to detail, visual design and editing really come through. This game has been meticulously crafted, and I love it. It's almost like a challenge just to enjoy all the fine details.
Contrary to my first impression, I now see that the movement is consistent. The puzzles are amazing. How does he do it? The learning curve is steady and challenging. Once you learn to use the map system, the game opens up. The little graphical details are delightful. This is truly a love letter to 2d platform gaming with a really well conceived and executed mechanic. Bravo!
Fez is not a clone of anything, and it is proof that the retro platformer can still be innovative. If I were to estimate the mechanical level of FEZ, I would guess playstion 1/Saturn/Nintendo 64 era, but it's hard to tell. The game is so dense, that I experience some slowdown at times, yet I have no problem emulating the PS1. The number of little sprite animations is awesome, and may just be a bigger processing strain than I give it credit for.
My one nit pick thus far is that I can't control the camera zoom. I'd like to get a closer look sometimes, but I am unable to do that. This is a bummer.
Also, this game brings to mind Voxels. I haven't played with them much except for the first Humble Bundle I bought, the Humble Voxatron Bundle. Voxatron was a fun little 3d shooter made of blocks, like Minecraft and Fez. What an interesting developement for 3d games: 3d blocks, rather than polygons. I'm for it!
I'm playing FEZ in a little bit of a different way than usual. Usually, I game in about 2 hour sessions, but with FEZ, I'm playing in half hour sessions. I like it. I find that I hit a wall at about a half hour, and rather than struggle, if I just put the game away, I will be refreshed the next time I start.
In conclusion: FEZ is very nearly a perfect game. It is rare to find a game with this level of detail, few come even close. A triumph of design and editing.
P.S. Many thanks to Daniel Featherstone for encouraging me to stick it out with FEZ.