Ahh, a question I've been wrestling with for ages! As much as I'd like to ignore some aspects of the TV show (i.e., the bizarre attempt to give Spike more development in "Eyes of a Spiketail"), I ultimately have to stick to the "canon-until-proven-noncanon" rule. It's not like anything in the TV show contradicts the movie series much.
I've always had reeeally mixed opinions on the TV show.
I love the episodes that brought old characters back with their original voices (Guido and Mo). Having Chomper back was fun, too, even though this was all but totally unexplained, and Ruby was a worthy addition to the group, though the lack of backstory on her friendship with Chomper is also really unfortunate.
Now for what really irked me: they had to keep giving old characters new voices that didn't sound a thing like the originals. Mr. Thicknose, Ali, etc.--those were the best replacements they could find?
Really?? If anything makes me want to call the show's canon status into question, it's the fact that Mr. Thicknose sounds 30 years younger than when we last saw him...but alas, I suppose low-budget replacement voice actors aren't a valid reason to de-canonize something.
Plus I'm still holding a silly grudge against this show for the fact that, when they started bringing a bunch of guest characters back from the movies, I kept waiting for the Rainbow Faces to make their return, and you know what? They never did!! 
I’d say the books and games take place around the times between the films that were released in between the game/book’s release. LBT doesn’t really need to follow a complex canon like other franchises.
well, some books, for example, don't fully follow plot of some films, as I remember.
Yeah, if a book strays from the plot of a film (like the original movie storybook that had a deleted scene or something in it), I don't think it's canon. But, hey, if you guys are looking to debate over something else of this sort, I've got an official LBT comic book that's an original story! (Where would I post pics of that?)
