Animated movies are a staple of any decade, having been a popular form of film since before the Hollywood 'talkie'. These days, there's a wide range of animation on offer too. There's still some traditional drawn cartoons, but there's also CGI, stop motion, photorealism and the influx of anime to the West to contend with.
Since the late '90s (and increasing massively over the last ten to fifteen years), animation has moved from being 'just for kids' to something for the whole family, and even something targeted specifically at adults. We're all just kids on the inside though, so there's a spectrum of movie moments here.
And moments is the key word. It's not necessarily ranking the best animated movies, but the most impressive/funniest/suspenseful/other adjective moments. It stands to reason that the better a film is, the more great moments it has, so the best of this decade can be found near the top. Cream rises and all that.
However, some pretty good movies like Tangled lacked a big spark, and so just miss out. Others might not have been that well put together, but had one great set piece that got them over the line.