If something is perfect, it't completely based on feeling. There's no such thing as "perfect", only "perfect for something", and even that is debatable. If we consider "perfect" as "99/100 perfect", the whole debate about SMG (or anything else for that matter) being perfect makes a lot more sense.
When someone says something being perfetc, it's a whole lot different thing, than something being perfect by definition. For example, there are few things in physics, which you can get closer forever, but never gain (could someone put this in an understandable sense), for example, C, vacuum, 0K, so they basically don't exist in reality, but they work as a frame. Same thing with something being perfect, you can get forever get closer, but nothing will ever be perfect and it does work as a frame.
What SMG is, as people have noticed, games today are supposed to be new, as in terms, that they feel like a new game, but also old, that they feel like the same games as before. And SMG is a perfect mix of these. It has elements from SMB 3 (actually SMG is more sequel to SMB 3 than SM64) and SM64, and it has it's own elements, which makes it feel like a new game within Super Mario frame.
SMG is perfect game, maybe the best game ever, or if it's not, it's atleast the best game in decade.
I don't undertand why people complain about swimming, it works perfectly. Even the camera works just like it should, it has certain "bad angles", but it fixed the "even worse bad angles" from SM64 and SMS.