I was kind of disappointed with the 2nd half of Mario 3D Land. I had heard people saying great things about it and new there was this other section of the game after beating the first 8 so my mind thrilled at the possibility of these extra levels. When playing the game, I found out that a lot of those levels were ones I had already played in the first 8 worlds but with a twist to them to make them harder. I did enjoy the challenge factor and overall still thought it was the best Mario game I had played since Sunshine but was bummed at the time that it wasn't a lot of new level content. It's one of the things I dislike about Super Mario Galaxy. It has a lot of repetitious elements and level portions it will have you replay over and over. (Although I'd later play Super Mario Galaxy 2 and that would become my most favorite Mario game since Sunshine so who cares about 3D Land.

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The Ambassador program was a pretty sweet deal. The NES games I never really cared about but the GBA games were an awesome bonus (although we had to wait until the end of the year for them IIRC). It is amazing that we never got GBA games on the 3DS eShop. We all expected it but it never came and they were released on the Wii U itself. It was either Chozo Ghost or TJ Spyke who would always post comments when people speculated about GBA games coming for the 3DS that Nintendo had made no such announcement and that a person was wrong to expect them. Well, it looks like he may be proven right all along in raining on everyone's parade but 6 years later and the possibility of GBA games on the system continues to fade.
The launch game I got for the 3DS was Rayman 3D. I'd always heard it was supposed to be a good game although Ubisoft had re-released it a lot. However, I thought the 3D effect in it was great and was the game I used to show people what the 3D effect was like on the system to try and hype it to others. I still love the 3D effect to this day and am disappointed that it has been treated indifferently by so many other gamers to the point that even Nintendo is releasing a 2DS with no 3D display after the NEW 3DS came out with it's better 3D capabilities. Of course, if I waited, I could have got Rayman 3D for dirt cheap but that was the case with pretty much all the 3DS launch software.
I later acquired Pilotwings for half off and I did enjoy it. Again, I liked flying in the 3D and it made me wish we could have had a Rogue Squadron type game on the 3DS. Even a port of one of the early RS games would have been great. The only problem with Pilotwings is that you just have Wuhu Island to explore and after you've searched it all through then the locale can be a bit boring. The hardest thing about missions is just getting a perfect landing most of the time as well. I beat it thoroughly despite its limitations and enjoyed playing it through a mission at a time though some craft were more fun to fly than others. I think it is worth taking for a spin and playing but it is limited in how much it has to offer.
I have Steel Diver and have heard some positive impressions about it since it's status as a launch title. I've meant to play it from time to time but still haven't gotten around to it. One of these days. From what I've seen and know of it, I think it might have gone over better if it had been an eShop exclusive like Pushmo or Ketzel's Corridors. But as a $35.00 (?) launch title, there wasn't enough there to keep players satisfied very long (unlike, say, Breath of the Wild on Switch). When Steel Divers 2 was released on the eShop, it seems like Nintendo seemed to realize this as well.
Really, aside from SwapNote, Videos, and Rayman 3D, the other couple things that define my first year with the 3DS was streetpassing to complete the Black and White Pokedex and the launch of the eShop Virtual Console and playing Link's Awakening for the first time. Now when I think of the 3DS, most of that stuff is kind of forgotten and I think of other games and titles to define it. That first year, though, was all about older games and odd applications.