I'm sure Sonic Rush Adventure is a good game. I plan to get it myself once the price goes down for it like every Sonic game. Seriously, just wait half a year to a year and you can get it anywhere for 19.99 or less. But like Brain Age 2, it seemed to get that same sort of vibe where it's a good game but it wasn't too different from the original and so people didn't talk about it too much.
And yes, I brought up mainly first party games but that's because Nintendo's the one that's really making the best games on the system. There are not a lot of 3rd party games to recommend. In fact, I went and took a look at the third party games I have for my DS. I've got 6 and they are:
Feel The Magic XX/XY
Zoo Keeper
Pac-Pix
Meteos
Trauma Center
Sonic Rush
Notice that most of them came out in the first year of the DS being on the market. Are there other third party games I'd get? Yes, Dragon Quest: Rocket Slime, Sonic Rush Adventure, Lost in Blue, Sim City, Contact, Cooking Mama, The Rub Rabbits, an upcoming Harvest Moon game and a few others but I won't keep listing everything. Again, only a couple have come out in the past year. Everything else is first year or second year. And I think that's another point. There seemed to be a lot more experimentation and fresh ideas when the DS first came out. So, even if a third party game wasn't the greatest, at least it could feel new or get a person to try it becuase it had a new concept or idea. But nowadays, it just seems like developers aren't really trying. They are just viewing the DS as a game boy with another screen to put a map on.
I just remember Jam Sessions. That also interests me and it's a new idea and use of the DS.
So, yes. I may pay more attention to Nintendo published games but that's just becuase there are more reasons to doing so.
As for your second point, it's not that great games can't cause great discussion, it's just that in the case of those two games, there isn't much to say at the moment. Professor Layton has been out for awhile in Japan and you can pretty much get any info you want about that game because of it. And as for Advance Wars, again, it's a not a game that causes a lot of discussion. The new artstyle and theme was interesting but in the end, it's still just moving modern weapons around on various maps. It's hard to discuss strategy when you don't know how the game actually plays or what kind of strategies can be implemented. I'm sure the Wi-Fi connection for the game will help cause some discussion as people play each other and discover things about the game. But in the end, it's just not a game that can really be talked about a lot before playing it.