I think the problem with this Animal Crossing is that most of the changes aren't easily noticeable. Sure there are more items, townsfolk, fish, bugs, bones, and the city, but some of the more interesting stuff that's changed isn't easily noticeable on the surface.
While not really a feature, everything has improved from past versions. This is especially noticeable when interacting with the townspeople. I have yet to run into duplicate dialog, (besides a few greetings and job requests) and feels much more natural as a whole. One of the coolest things I've had happen is Ruby (the neighbor rabbit) stopped me and commented on the specific type of sunglasses I was wearing. All the residents seem to have personal preferences about the other residents as well, and you can really see who's popular and who's not in town.
This might be a small adjustment, but they finally let you design clothing in individual sections, so that you now have quite a bit more freedom in what you make. I know this was just a huge deal for me as in the previous Animal Crossing I was a pattern designing fiend.
What may be the coolest thing, however; is that if you walk a common daily routine enough you'll eventually wear a path in the ground. This isn't something that happens overnight either, but can take up to 3-4 weeks before you start seeing noticeable results, and up to two months before the grass has been completely worn away. This is the type of thing, where your actions effect your surroundings in subtle ways that I hope they've more of.
So while core game play may not have changed much, (you still do the collect the furniture and pay the mortgage thing) calling it a cheap cash in or the exact same game really doesn't cut it. Especially if some of the best parts of the game haven't been found out yet.