Is the setting and planet for Anima universe Earth ?

Yes, it is in the far future. There was some giant cataclism where we lost all out technology and long slumbering of magic woke up. That is the very beginning of the long history of Gaia.

Think like Sword of Shanara world.

Not necessarily.

It might be just as Hrathen says, but until the Anima Studio actually declared it in the Spanish forum, I wouldn't consider it a certainty.

Surely men forgot. It's not even known if they forgot due to a war, actually. It's suggested, not given for sure (after all, since people forgot, there's no way to know how they did).

It might also be an alternate universe where somehow some aspects of our history are modified.

It's not uncommon for other settings having similiarities to our own world. To give you an example, the Forgotten Realms sport Tyr among their deities, who is a deity somehow present in a religion which existed in our very own world (the religion of medievil german tribes).

I guess that is true. The books never come right out and say Anima is in the future, but it is a future. Before the Cataclism there was technology at least as advanced as modern Earth's. Actually since some groups have access to this (ancient) tech some of their tech seems better than ours.

I guess placing it on earth or placing it somewhere else that has an earth like ancient past is up to you as the GM

I tend to think of all RPG worlds as worlds parallel to ours, as in The Dark Tower books by Stephen King. Then you'll always have a good excuse for things that are similar to things our world. Like religion, weapons, languages and stuff. It has worked pretty well this far, at least.

All role playing settings are fiction so aren't really are world. But sometimes you pretend they are.

Chuulu is supposed to be this world. So is any role-playing game based around spys or espianage.

D&D obviously isn't out world.

So as much as any game is supposed to be our world (despite the fact that it isn't because its just pretend) I think Anima is supposed to be in the far future of our world.

the world map and cultures are very inspired by our world, but the supernatural elements (wake, magic, secret organisations) make it very fantasy and far from our reality, I think the author, creating all those complicated elements wanted the players to have a basis with the known world and not create an even more complex world with a different map and complex cultures

The only thing sure, is that Gaya is the "future" of a human world which at some point had achieved an extremely advanced technological level (but probably no space-travel, which is odd for such an advanced culture), had some sort of holocaust (possibly a war) and was later influenced by the arrival of a bunch of gods that started meddling with it, finding it interesting. ALSO it's implied that magic has always existed in Gaia (actually almost all of the most advanced ancient technologies are arcano-technologies developed with the mixed use of science and magic, meaning that magic must have been mastered even before man forgot). This alone would be enough to exclude that Gaia is our world future.

Considering the current state of our technology and our tendency to space exploration, if we reached Imperium/Solomon technology level we'd probably send space ships around way before the "holocaust" occurred. Probably our "holocaust" shall occur way before we reach Imperium technology, actually...this is another hint that Gaia shouldn't be the future of our exact world...UNLESS we suppose The Imperium is an organization composed of men who lived in some space colony and so they were unaffected by the great "holocaust" that shook the men on Earth. Still it makes few sense, if you consider that Duk'Zarist and Silvain have similar organizations whose superior technology cannot be explained the same way.

All this comes of course from mere speculation.

PS - The therm "holocaust" here does not refer to any real world historical event or religious concept. It's just a useful word to describe what happened, take it like that.

Any science, sufficiently advanced...

It's quite possible that the "magic" that we see in Gaia is the product of a science so advanced that it achieved total noninstrumentality - that is to say, the "technology" now sits resident all around us, dormant until we activate it (or, perhaps, it's already inside us). It's also possible that the "gods" are transcendental creatures created by people before the cataclysm - they're the "ascended artificial intelligences" of the world. And the non-humans are humans, or more correctly transhumans.

On the other hand, I may just be blowing smoke.

The long and the short of it is, they left an opening for you to think what you will, and the answer to this question is probably more up to the individual GM than to Anima Studio.