Just out of interest, what do you mean by "spirit"?
There's this Toriyama quotation which says something about his every page being ruled by "Look at this, over here, it's so much fun!" It's like the Olivier quotation about every moment on stage being consumed by "look at me, look at me, look at me."
If you look Toriyama's work, in general, there's usually a pretty quick pace, not too much introspective belly-watching, and most of the story is told through facial expressions and gestures rather than exposition. No one is taken too seriously, even the characters who take themselves too seriously... and it is, of course, supposed to be a humorous strip, but I feel like a lot of manga really tries to get people's attention by blowing things out of proportion and making little moments far larger than they have to be.
That gets really dull after a while, as you read through contrived plots filled with familiar jokes and very little of its own feel. I don't feel like the author is saying "Hey, look at this, this is really important, hey, hey!" With a lot of manga, it can sort of seem that the author is bored, or doesn't care that much, or isn't telling a story that really matters to them... the story doesn't follow their own sensibilities, but the sensibility of whatever's popular at the moment.
I don't know quite how I feel about FMA. I wasn't very drawn to any of the cast and I didn't find it funny (since a lot of it seems to be short jokes and eating jokes, which I've basically lost interest in at this point unless they're executed in surprising situations), so I put it down pretty quickly. It had an interesting opening, but then the characters just didn't do it for me... I only really found myself interested in the things with Ashbal, not any of the rest of it.
Somehow, I feel like the light touch the author takes with the subject material to keep it Shonen-Jump material sort of ruined it for me. It could be a good serious story, but as an adult (?! When did this happen?) I don't find it appealing.