Honestly I feel the same way about them using those properties. We all saw Nuts and Bolts. We all know the story...
As for your question...Sonic Adventure 2. Yes, I fully realize it's purely because of nostalgia, but this is my answer, and I'm sticking by it.
...How many non-smash bros amiibos do you guys think will become available? I've been noticing a trend of Nintendo pushing solely Mario, Zelda, Animal Crossing, Pikmin, and Pokemon stuff as of late, so something like a WALUIGI amiibo isn't too unrealistic...but what about other properties? Think we'll ever get, say, a Wolf Amiibo, or a Ridley Amiibo?