Hm. It's not necessarily better.
The older ones for instance have more detail. Better shadows especially.
New one looks pretty bad. Has lines on his knees. Is overall flat. The right most fold of Charizard's wing has no shadow despite being 1. folded and 2. the under section of the wing, giving for more shadows. This does not correspond with physics or real world lighting. The thick outlines also lend to a sense of amateurish feeling. The only thing that could be construed as "better" is the flame, and Charizard's more stylish flame in the older one is much more consistent with the art style. Throwing CG on top of 2d animation does not make it look "better".
Left: Charizard's skin highlights in the correct positions. THe right is again, flat. The outlines, again, make it look out of a coloring book. Shadows are decent in this one, but noticeably more lazy compared to the original. Instead of having the shadow envelop his stomach, end at the arm, and draw a new arm shadow, it's one long shadow. Lazy and cheap.
This comes down to personal preference but I again, prefer the original. I prefer the more Earth toned and darker contrast of cel. I dislike forced bright colors of digital immensely. Further, again, too thick outlines.
This is fantastic digital and superior to the original.
Cel Misty looks much better than digital Misty. The eyes are drawn in a more detailed and stylish manner. Digital Misty's eyes look like a doodle. That hyper stretched vertical iris of Cel Misty is excellent eye stylization and exudes character. There are also inconsistencies within the hair on Digital Misty. Hair shadows cut randomly, rather than canvas the mass of her hair like in the original. Comes out obviously looking like vectorized object. The result: flat character. Look how the outlines of Cel Misty allow her to soak into the environment like she BELONGS there. That's HER world. The thick outlines on Digital Misty make her look like another prop. She doesn't belong there, she's standing out and does not blend into that forest.
Digital version has no sense of presence. Despite apparently raining, you cannot see make out a single drop unless you're looking for it. Could be a bad cap, but still. Background on digital is great. The rock is especially great in terms of detail and on the ball. Characters again, have a loss in detail. No shadows under Brock's vest pocket, absolute zero shadows on Ash's raincoat despite being a rainy, storm setting, shadows on Charizard's blanket can literally be divided into three shapes, Brock has zero shadows just like Ash even where he should have some (i.e. under his arm fold). Outlines are, again, shit. The characters stick out and don't blend into their world. The cel version tells a story. The digital one looks like it's happening before the story even starts.
This perfectly encapsulates how Japan went cheap with their animation. Even Pokemon looks worse. Digital isn't inherently bad, but over the years, they have lost passionate artists to other industries. And now you get this: lazy, flat, boring animation without any presence or any detail. Just flat characters and basic settings. Lazy, cheap, infuriating.
Kill La Kill, for all my problems with it, is a show of passion. That's digital done right. Digital has all the ability in the world to look better than cel, but it rarely does. Because there's less need to spend time on it, the animation suffers. Why bother putting time in to it if you can rush out an episode like it's nothing? Saves money, but doesn't create quality.
