I think it is important to remember WHO they are targeting when they release a commercial for a game.
"Gamers" will already know about what games they are interested via the internet ( written previews, youtube etc), gaming podcasts, gaming magazines, seeing posters/etc in game shops etc. That is why when you see a commercial for a game on T.V (I know Assassins Creed did some, Animal Crossing did some in the past like already talked about in this thread) they will often be extremely general and not necessarily show you the game, but more try to invoke a "feeling" out of the casual watchers. For Xbox360/PS3 game commercials will often times be overly cinematic in order to rope in more casual or "out of the loop" people.
I remember my best friends 50-something year old mom wanting Animal Crossing City Folk after watching the commercial that many people in here are dismissing as being awful. I agree, it is not that great but it isn't to target people like us.
Here is the Assassins creed 3 commercial I was thinking about:
https://www.youtube.com/watch?v=DEYdiB0824I
Really cinematic and doesn't show a lot of the game. I think most game commercials are modeled after something like this.
I think though they will start to pick up with advertising New Leaf a bit more when it gets closer to the release date. Maybe like late April or so. I know they advertised New Leaf here in Japan around release date (like late October to late November), same for the Wii U.