I choose my starter based on looks, and Rowlet is the only one that really looks decent right now, as the others look sillier than Bibarel (I love Bidoof, but Bibarel is weird). We'll have to wait for the evolutions to get revealed, but I'm hoping Litten gets a cool evolution, because cats are A++ (although I do have to point out that with the Litleo line [lion], the Sun legendary [lion], and the fire starter [cat], we'll have 3 varieties of fiery felines [two steps closer to matching all the fiery canines {Vulpix line (fox), Growlithe line (dog), Houndour line (dog), and Fennekin line (fox)}).
Popplio is amusingly close to "Polio", though I doubt Nintendo will let us name it that (if we can, feel free to endorse my idea to all your friends).
As for legendaries, they look a bit sub-par compared to the others, but the ridiculous-looking vampire moon bat is amusing compared to the sun lion, so I'm 99% sold on Moon. (I found the boxart on bulbapedia, and I noticed both have some sort of thing over their eyes that looks like a helmet or something, while the eyes kinda remind me of holograms. As unlikely as it seems, I hope this will tie into the stories somehow [more space/alien-based pokemon, like Deoxys? [I know there are more Pokemon like that, but Deoxys is the most "alien-looking" so far].)
The region looks nice, though small, so I wonder where all the towns and such will fit. From the information provided on bulbapedia and a google search, it appears Hala will not be following the plant-naming convention, although googling "Kukui" gives me results for a type of tree, so maybe Hala's an assistant? ([tinfoilhat]If Hala is, in fact, the professor, I bet he'll turn out to be a phony, and the villain in disguise.[tinfoilhat])
Graphics appear to be less chibi-style than gen VI, which is refreshing, since each gen has been doing well with introducing new graphic features. (I can't lie, I was subconsciously expecting the graphics to be like those of X/Y/OR/AS, though Nintendo certainly proved me wrong! [I don't know why I was thinking that, though; gens 4 & 5 also shared a handheld, but had different graphics. I haven't really been following the Nintendo scene beyond snippets of news, so my expectations were probably lowered from the other game companies I follow.])
I'm not one to care about or pay too much attention to skin tone, but a notable amount of NPCs shown have darker skin than our pasty example protagonists, which makes a lot more sense than lighter skin in the setting (based on Hawaii). While it's likely due to marketing or aesthetic reasons, I can't help but think the example protags use absurd amounts of sunscreen.
Well, with the "Global" and European release dates of our lovely Gen 7 confirmed, it's time to theorize the Gen 4 remakes! But there's a time and a place for everything, so I'll refrain from biking indoors =w=.
EDIT: All the starters are rather adorable, but the trailer made the water and fire types look kinda silly. Hopefully, we'll get better looks at them as they appear in the games, soon.