The original Astro Boy TV series had a very low budget. The animation from what I was told was done on 4's, 6's, and 8's... Because of this, the animation/movement tends to be very choppy in that show. It's a show that's best appreciated on the strengths of characterization and plots than it is the actual animation.
For anybody that doesn't know, most (traditional) Disney feature animation was shot on one's meaning for every bit of movement a single drawing was exposed once so in theory 24 drawings per second of film were created. They didn't always do 24 drawings a second but that was the standard. (Even Disney likes to save money and they DID cheat once in a while when they could get away with it.) Warner Bros and other animation studios generally shot on 2's (2 exposures per drawing) for their animated shorts to save time and money and the animation was perfectly fine unless they had to do zoom's or certain kinds of movement (running, diving boards) that had to be done on 1's. What Disney did was sort of overkill unless there was a really good reason to do animation on 1's.
Anime is usually done on 4's or more (in the case of Astro Boy to really, really save a lot of money!) unless it's required to do more drawings for specific movements. That's why there are a lot of still drawings moved across screen and a lot of camera moves and background effects. They're basically fooling people into thinking there's more movement onscreen than there actually is! When you really pay attention to anime, you see a lot of backs of characters (and no mouths) when they're talking or characters just standing there! (There's a joke that the characters in Dragonball Z did more standing around and yelling that they were gonna rip the other guy apart than actually fighting! That literally was true!) The stillness is also why the drawings in anime TV productions tend to be more detailed and colorful than their American TV counterparts were. Most anime features also have very limited animation but because of higher budgets they can take more time to do decent animation when they have to AND draw and color better than most TV shows.
I've read that quite a bit of money was spent on the 2003 Astro Boy TV series. I think the budget per episode was ridiculously high for an anime series -- they were banking too much on the Astro Boy name to make money. It was not a huge hit anywhere from what I've read. They have never seemed to equal the popularity of the original Astro Boy TV series... I don't think even the 1980 revival (which was the last Astro Boy TV series supervised by his creator, Osamu Tezuka) was as well-liked as the original. Astro Boy is sort of like Mickey Mouse. He's recognized as an iconic figure BUT nobody working in the anime industry now (that cares about the character) quite knows HOW to recapture the essence of what made the character work in the first place with ANY consistency and they've had a hard time trying to recreate the character for newer generations...