When I think about this topic, the three that come to mind are: Bob, Stitches, Lucky. I know friends who have never even played AC but know of Stitches and Lucky.
Among the villagers, Goldie or Rosie, probably. Goldie is one of the first villagers in the spin-offs and sometimes used in tutorials. Rosie was a major character in the movie.
Personally, my first thought was Peanut. But her media presence is limited to the cover of Wild World (along with Kiki, Stitches and Ruby), if I remember correctly, and it doesn't help she was in my WW town for years and as such is a staple for me.
However, as she hasn't appeared that much in merchandise besides WW, I will have to go with Rosie, Goldie, Fauna, Bunnie, etc. because of all the reasons everyone above has already laid out.
Peanut probably is too pink? Though the same could be said for Bob, and he has his presence maintained just fine. I think in general, the more nature looking villagers are used more in media generally.
Isabelle is a prominent face for Animal Crossing and she has not been in the series since the start so I do believe that newcomers have a chance at being the face of Animal Crossing.
That said, I think Stitches has a very memorable look to him, but because of the cartoon I think Rosie is up there as well.
I would have to go with either Rosie, Bunnie, or Goldie. All three have been on many titles of the AC series and are on many official AC products. They also have very easy going and friendly personalities that naturally appeal to children. I'd say the most recognizable and memorable out of the three would be Rosie since she has funny over the top facial expressions and has a cute and simple design.
The first one I thought of is Rosie, but I also think Goldie can be as well. I feel like any of the villagers heavily promoted for Amiibo Festival fit the face of the game well. For me personally, I’d like to think it’s Bill.