I might end up being an odd one out here
I'll get a few obvious ones out of the way first so I can disqualify them for being too easy as picks: the first movie's animation soars above everything that came after; the craftsmanship of the art and movement is extraordinary and the color direction is great; and the bulk of the TV series' animation is firmly at the bottom; no slack to be cut there, it's a bunch of crap.
From there, I think there are more, finer divisions to make than just pre/post-art shift, though that is still the defining line in all of this given how much changed after that (e.g. the
T. rex designs). The pre-art shift sequels can be split up into two eras, one adjacent to the Roy Allen Smith-directed movies - the style in question is janky and limited but has a certain charm to it thanks to the decent artwork, the colors are also pleasant - and one adjacent to the Grosvenor-directed ones - they must have changed animation houses and it shows, the animation is even worse and the art takes a hit; the colors are inconsistent between the two movies, they're awful in
V and relatively fine in
VI.
After
VII and the art shift, I think things splinter:
- The seventh movie is in a weird place; the animation itself is leaps and bounds above the previous sequels (especially the last two), but the art style is like a weird prototype for the later sequels, one with no shading whatsoever.
- The eighth, ninth and tenth movies all have a relatively consistent style; though I'd argue the animation itself is a hair below the seventh movie, the colors and art are definite improvements, with more agreeable colors and actual shading. I'm hard pressed to say it's good but it's decent for what it is; it's also worth noting that there's variation even between these three movies, especially with their use of extremely poor CGI (VIII uses very little, if any, IX flexes its muscles in that regard and X goes to town with the stuff).
- The eleventh movie tries to be a lot cartoonier than its precursors and fails miserably. This is most egregious in the climax where everyone turns into jello monsters while running away from the sharpteeth. Everything on display here is unappealing, I'd argue it's as bad as the earlier sequels but for different reasons.
- The twelfth movie does a fine job for what it aims for; it uses a lot of bad CGI, sure, but the animation is a lot more stomachable and the art is decently similar to the earlier post-art shift sequels, albeit with duller colors.
- The thirteenth movie is weird; all in all I'd say it's akin to the gasps of half-decent animation in the TV series, though it's still far from great and it dips in plenty of places. Worth mentioning is that the thing is utterly rife with animation and coloring errors.
- Journey of the Brave's animation is stilted and bad; the art is definitely off in places too. On a technical level, it's probably the worst of the 21st century sequels, though I'd personally rank it above XI, at least.
I'd say my favorite animation style of all of the ones depicted in the sequels is the mid-post art shift style depicted in
VIII -
X, though I'll readily admit that it's flawed.