Like Highlander, there can be only one!
I don't think there's any discussion to be had on the idea of whether Inception was all a dream or not. Here's my reasons:
1. If it was all a dream he doesn't really get back to his kids, so the movie loses it's meaning and pay-off. Not just that, but none of the events in the movie really happened at all, and the only real person in it was Cobb. How is this better than a face-value interpretation?
2. The only thing the filmmakers themselves put into the film that hints at the interpretation of it all being a dream is the ending. And we all know that was merely a technique to bait online discussion and word of mouth and shove in some ambiguity at the end.
I would also not call the animatrix that shallow. More shallow than it could have been, but definitely not on the same level as the sequels. But it is true, and I already felt, that the second renaissance is very straightforward, a mere morality tale on treating robots right because obviously humans would never put any value in (near-)sentient beings they created. But segments like Program, Final Flight of the Osiris, Kid's Story, World Record, Beyond, A Detective Story, and Matriculated are pretty straightforward too. But they were never meant to be that kind of story. Maybe Matriculated raises a question or two, though, but I never much cared for it.
Edit:
"What the king dreams, the hand builds."
Sorry for the shitty pic.