And as for LeSabre's point of them over hyping the games:
They have to.
These are brand new games. New Pokemon, new features, new everything. When it comes to GF releasing a new thing, or any company releasing something new, you kind of have to be super excited of it. If you're not proud of your product, your customer won't be excited. As far as using Arcanine goes, it is a VERY well known Pokemon. My mother even knows it and she only knows three Pokemon at best. Using such an appealing Pokemon in their trailer only makes the consumer more excited to see more of this game which can potentially lead to the purchase of said game.
To be honest, it makes sense that they would use Arcanine, as random as it seems. Yes, Emboar may have been slightly more appropriate, but if they want to show that they have included Pokemon from the previous generations into the games, this is a good way to go. Yes, they did show Seviper and whatnot, but you also want to show the hero of the game having a Pokemon from another generation as well, such as Arcanine and Lucario.