I was curious about this so I went and listed the NA releases in the first two years and two months for both systems (DS and 3DS) and the total is pretty even without including most of the 3DS eShop games.
168 games for the DS vs 162 for the 3DS. So if we are talking pure quantity the argument doesn't really hold up as it is pretty much the same.
Regarding quality, we could look at metacritic average for both lists but that would take quite a bit of time unless there's a convenient way of doing it on their website that I am not aware of. We could also look at what kind of games both libraries were made of two years into their lifetime, which could give us a clearer image and that's what I did. I'll start with the games that most posters here don't care about so we get them out of the way:
Licenced games (based on popular movies/books/toys/shows) and that are often targeted at a young age audience are about at the same count.
44 for the DS vs 38 for the 3DS. Included in this category are games such as "
Harry Potter and The Goblet of Fire", "
Nicktoons: Unite!", "
Disney's Chicken Little: Ace in Action" for the DS and "
Thor: God of Thunder", "
Wipeout 2" and "
The Adventures of Tintin: The Game" for the 3DS. Titles most here I guess don't care about but I must mention that included in the 3DS count are a few LEGO games too.
Another represented group are minigames collections and low budget puzzle games:
16 on the DS versus 23 on the 3DS. Included in these are the Brain Training series on both consoles. Other titles include "
Battleship/Connect Four/Sorry/Trouble" for the DS or "
50 Classic Games 3D" for the 3DS.
Racing games are at
8 for the DS versus 7 for the 3DS while sports games are at
7 vs 6. In both cases, it is often the same series that come back such as FIFA, PES or Need For Speed. It's interesting to note that 3DS has a Madden game, a Ridge Racer and a WWE game.
Games such as Nintendogs are at an even count too. 7 versus 8. 3DS also has a lot of "fashion" games which were non existant on the DS at the time, stuff like "Imagine Fashion Life".
Now let's look at some of the major "core" games in both libraries and compare:
Code:
[B]DS[/B] [B]3DS[/B]
Super Mario 64 DS Super Street Fighter IV 3D Edition
Advance Wars: Dual Strike SMT: Devil Survivor Overclocked
Castlevania: Dawn Of Sorrow Harvest Moon 3D: The Tale of Two Towns
Phoenix Wright: Ace Attorney Mario Kart 7
Mario Kart DS Tales of the Abyss 3D
Mario & Luigi: Partners in Time Tekken 3D
Animal Crossing Wild World Metal Gear Solid Snake Eater 3D
Metroid Prime Hunters Kid Icarus: Uprising
New Super Mario Bros. Kingdom Hearts 3D
Dragon Quest Heroes: Rocket Slime New Super Mario Bros. 2
Yoshi's Island DS Zero Escape: VLR
Castlevania: Portrait of Ruin Professor Layton & the Miracle Mask
Phoenix Wright: Ace Attorney Justice for All Harvest Moon 3D: A new Beginning
Kirby's Canvas curse Fire Emblem Awakening
Children of Mana Super Mario 3D Land
Final Fantasy III Etrian Odyssey IV: Legends of the Titan
Luigi's Mansion Dark Moon
SMT: Soul Hackers
DKCR 3D
Animal Crossing: New Leaf
Monster Hunter 3
Castlevania: Lords of Shadow
Starfox 64 3D
I think it is safe to say that at this point the 3DS has more "big" quality core titles than the DS at this point in its lifetime and in more different genres.
On the other hand the DS has had more smaller quality "core" games such as:
Code:
Wario Ware: Touched!
Yoshi Touch & Go
Polarium
Pac Pix
Trace Memory
Lost in Blue
Trauma Center
Metroid Pinball
ElectroPlankton
Super Princess Peach
Elite Beat Agents
Hotel Dusk: Room 215
The 3DS on the other hand does have a few quality games that can compare to these. The rythm games selection is superior for example with Theathrythm, Rythm Thief and Harmoknight. There's also games like Steel Diver and Pilotwings resort that compare very much to the style of the games I listed for the DS but most of these games are now on the eShop. Stuff like "Pushmo/Crashmo", The Guild games, etc. So if you consider the eShop the libraries seem to offer about the same quantity/quality for these kind of games, if you don't, I'd say the DS wins this particular battle.
Of course these categories are highly subjective but I tried doing my best at being as neutral as possible. Games list is from Nintendo's website so I might have missed a few but overall I think it gives a good overall view of what both consoles games libraries were 2 years after launch.
Personally, I think the 3DS has a stronger library. Most of the popular IPs in the early life of the DS have seen sequels on the 3DS or have games announced in the future (both first part/third party). The question is if the 3DS will be able to carry its momentum through the next few years. In comparison, the DS library only kept getting better with time.
So to answer the question OP asked, no I don't think the 3DS is succeeding for unconventional reasons, especially if we consider the DS success as the conventional one. Both libraries share a lot of similarities with a more "core" focus on the 3DS.