I'd enjoyed Tomodachi Life more than I'd expected when I played it earlier this year. The game isn't that deep, but I enjoyed the quirky humor and it was fun to check in on my Miis to see what they were doing and intervene in their love lives if needed. It looked like Miitopia, also for 3DS, was like Tomodachi Life but with RPG mechanics and a story, so I was interested in checking it out.
I was hoping the game would have the same level of absurdity and surrealism as Tomodachi Life, but the laughs are definitely fewer and further between in Miitopia. You can cast Miis to specific roles, such as your main party (warrior, mage, cleric, etc. as well as more-unique classes such as pop star and cat) as well as NPCs. The game makes it easy to import Miis from your 3DS's Mii Maker, Tomodachi Life save file, or QR codes from software such as Miitomo, or pick from user-submitted Miis.
The game is a super-simplified RPG, which is actually fine by me as it makes things much more streamlined. Towns are completely linear and in 2D seen in profile (like Zelda II: The Legend of Link), and you can only move left and right. You don't actually explore dungeons but instead select points on a map and then at the occasional forks decide if you want to take the left or right path. Battles are simplified and you only have to worry about controlling one character, but the AI does a completely competent job with the other characters in your party. Even shopping for new equipment (weapons and armor) is simplified. The game just presents you with the option to upgrade to the next highest piece of equipment, which always has a higher attack or defense stat than what you currently have.
The game has a typical RPG loop where you buy equipment, explore an area, encounter battles, and then return to an inn in order to buy more equipment. Miitopia adds a couple of more-unique mechanics. For one, you choose which characters you want to room together in the inn, and developing characters' relationships gives you important bonuses during battle (for example, a Mii may warn another Mii about an attack, giving him/her a chance to dodge it). The game allows same-sex pairings, which is great to see and feels like a step forward. You can also control your characters' stat growth via food, which you derive from defeated enemies. As with Tomodachi Life, characters will have their preferences of what foods they like, although they can't be predicted so you'll have to discover their likes through blind trial and error. It's pretty obvious what stats you should focus on for which characters (e.g. increasing magic for the mage), but it makes growing your characters a bit more active.
Occasionally your Miis will act out a little skit as they travel, which are generally amusing. The visuals are pretty simple and plain, but anything more complex would look out of place next to the Miis. The music is pretty standard RPG fare, as is the battle progression, enemies, and plot. The game lets you fast forward through battles, which helps alleviate the boredom. There are some visual gags that were hilarious, like the flamboyant movements of the Pop Star, but even though I enjoyed seeing my Miis in a new context the game gets repetitive quickly. More of the whimsy seen in Tomodachi Life would have really helped keep my interest, but as it is I found myself having to set this aside after the first "chapter". [Minor spoiler: The game is divided into distinct sections, and at the beginning of each section you're forced to restart at level 1 with an all-new set of companions, which seemed very annoying to me.] As with many RPGs the game seems like it's fairly lengthy, but given how repetitive it is I probably won't be picking it up again anytime soon.