I've bothered to compile a list of Wii U games that I believe use amiibo well, ones that don't, and ones that exist in a sort of limbo for me. These aren't all of the games that use amiibo, but they are most of them, for sure, and the most important ones too.

Good Use of amiibo - These aren't harmful or detractful in anyway.

Smash Bros. for 3DS and Wii U - The best use of amiibo, IMO. Probably the only reason amiibo exists, and everything after this game was afterthought. The fact that you get to have your own little customizable, trainable AI with you, stored in a little figurine that you can take around with you and battle with on other copies and consoles versions of the game is cool on its own. That was the potential cap for amiibo, most probably.

Mario Tennis: Ultra Smash - Same as Smash, basically. But not as good of a game to use them on. However, you can use them in the online modes to battle (if you call playing tennis "battling") alongside you, which is one thing it has over Smash.

Mario Kart 8 - The changes made by amiibo are completely aesthetic, and don't add anything to the overall experience that detract when taken out. It's just a nice little bonus for having the amiibo. Just a little costume for your Mii based of one of your favorite Ninty characters. Nothing wrong with that.

Yoshi's Woolly World - Pretty much the same as the game above, only difference being that it's compatible with almost every amiibo that was availiable at the time of launch. Yippee.

Captain Toad: Treasure Tracker - Toad amiibo provides a little bonus minigame where a little 8 bit Toad amiibo is hidden throughout each level of the game. Doesn't really add anything major to the experience. Just a little bit more to do. Other amiibo give you 1-UPs, which is fine by me.

"Ehh" Use of amiibo - These aren't that terrible, but aren't exactly good. That, or they do some good, but are also harmful/detractful, which is bad, m'kay?

Splatoon - They provide challenges based on the single-player levels. They are basically the same levels as in the single-player, but you are using a different weapon-type. Being allowed to use different weapon-types in the single-player feels like something that should've been in the game already. They don't just straight-up let you use that weapon type in every single level, which saves it from being awful. You are also unlocked new gear and weapons upon completion of these challenge stages, but they aren't anything special at all.

Hyrule Warriors - Link amiibo unlocks a completely new weapon, the Spinner. That kind of content shouldn't be amiibo exclusive, but it's just another weapon on top of everything that Hyrule Warriors already has. Other amiibo can just unlock generic weapons for you, ones you probably have. No big deal, overall. 

Super Mario Maker - amiibo unlock new costumes, a mostly aesthetic aspect. These can even by unlocked in game, so that's not bad. However, the 30th Anniversary Mario amiibo unlocks a completely new power up, and it can't be unlocked in-game. You don't just lock a new feature of level experimentation and creation in an amiibo, and it's especially bad because it's a game about creating to your imagination. Even worse, this special power-up does more than any regular power-up.

Twilight Princess HD - You can use the Link amiibo to get your arrows refilled, but only once per day. The Zelda amiibo will give refill your hearts, but again, once per day. Ganondorf will make you take double damage. I think that making the game harder for yourself shouldn't be locked in an amiibo, but hey, Hero Mode is an alternative, I guess. The Wolf Link amiibo unlocks a new dungeon. While it's nothing special, you shouldn't put that in an amiibo. Reasonably, the full physical $60 package (the only one you can buy right now) contains the amiibo in it, so no biggie.

Star Fox Zero - Fox amiibo unlocks a retro Arwing skin, which is cool. Falco amiibo, however, unlocks the Black Arwing, which makes you take more damage, but deal out more damage as well. Feels like something that should've been in the game to begin with, as an unlockable. Who knows, maybe it is an unlockable too. IDK. No one knows.

Terrible Use of amiibo - These games should make you angry for having this kind of amiibo support.

Mario Party 10 - In a game that's already so mediocre, they just HAD to lock an entire mode behind amiibo. Too bad it's the mode that most resembles what fans wanted from the game, even if they somehow still managed to screw that up real badly too. 0/10

AC: amiibo Festival - ¯_(ツ)_/¯ You should know this by now. The fact that it's an "amiibo-based game" is just the salt in the wound for this horrible excuse for a holiday release.

Conclusion - 5/12 games I mentioned here make an entirely good impression with amiibo in my eyes. Look at that number anyway you want, you should know they didn't have any really cool ideas for amiibo beyond Smash.

I would have loved it if they had continued with the idea of Amiibo's storing information about our gameplay. I love Metroid so, for example, if the Samus figure could have recorded the inputs from your control pad in Super Metroid then you could start the game again and let the Amiibo retraverse the your speed run/adventure. Recording your game with a figure would have been really fun. But I waited and never saw one reason for me to get amiibo.

They should have just made Amiibo unlock content early than have content locked on disc without it. Even their investor meeting shows that most people collect them as collectibles anyway so there's no lost in devaluing their purpose as a cheat code to unlock early content. Amiibo locked content is ONE (not the top) of the worst dlc practice from the game industry so far.

I know the game isn't it out yet, but let's not forget about Kirby Planet Robobot.

The fact that you need a Kirby amiibo just to unlock U.F.O. Kirby is pretty dumb.

Tphd goes in the bad usage and SF it's still to confirm, but in case it's confirmed it goes too on bad.

I think there's too much bitching and whining about content and Amiibo.

Cool idea, but the storage needed to record all that would probably make Amiibos way too expensive. 

SMM does lock an entire power-up behind the "amiibo wall", one you can't get in-game, so I can't put it under good. But the amiibo costumes are neat, so it's not bad at all.

The content Splatoon unlocks is just a retread of single-player levels, just with different weapons to choose from, so it's not like it's committing any horrible crimes. Also, what you get from beating those challenges isn't all that special. It is really aesthetics-based at that point.

In Splatoon, you get individual pieces of gear and equipment for your Inkling for beating levels, but the way that gear works in the game, it's the same as anything else, just visually different. The weapons you get for beating all the challenges are just reskins of basic preexisting weapons.

In Mario Maker, you can only get a certain powerup that turns Mario into a giant 8-bit version of himself by amiibo. Which sucks, because the power-up is really neat. Changes Mario's physics, allows him to smash through walls and break platforms under him.

Precisely. I actually own it.