Favorite Games: Super Mario 3D Land, New Super Mario Bros 2, Mario Party series, Pokémon series, Fire Emblem series.
This device features most of the greatest games I've ever played on a Nintendo Console, and it's 3D functionality made it so extremely immersive (although too immersive for some people) as it features 3D content without the need of wearing anything! It's the first Nintendo handheld that features a joystick (and a second optional joystick add-on for specific games). The speakers can get very loud and they have been fine tuned which results in loss of bass compared to the Nintendo DS, however this makes sense because I could only hear bass with my ears on the speakers on these older devices and not from far away. 3D audio works exceptionaly well and it's impressive the device could run games at such resolution when 3D is turn on (it renders the upper screen twice with a little location shift if 3D is enabled).
Speaking of the screen quality, it came with even better screen colors than previous devices, however this depends on model, some devices came shipped with a good IPS top screen and other with a TN top screen. My red model came with a TN screen. The stylus that came with it, was the best one I ever used, the best thing about it is that it can be stretched in and out. It came with 2 cameras on the the back which allows you to make 3D pictures and videos. The microphone feels like it has slightly improved compared to the Nintendo DS and DSi. The inner camera is used a lot with in games and software with face recognition, for example in Pokémon X and Y when interacting with your pokémons!
I found the audio out to be placed at an unusual spot, however I did not use it that much. It ships with a charging cradle in which the system can charge, it has a small opening at the spot where the audio out can be found of the 3DS allowing it to be grabbed very easily using your thumb.
Games
Super Mario 3D Land
The first time playing this game was one of the best experiences I had in my life, I didn't play Super Mario Galaxy yet at the time, and was only familiar with Super Mario 64 as 3D games, and the amount of powerups and levels it featured gave my so much inspiration for my own games. It gave me unique dreams at the time and has become a very nostalgic game for me.
New Super Mario Bros 2
It was just what I expected it to be: A follow up to New Super Mario Bros DS! It features the leaf powerup and other new things such as gold powerups and lots of coins and very good use of 3D for example the backgrounds. It features solid gameplay just like it predecessor.
Mario Party Series
This is where the handheld Mario Party games got much better, the DS version suffers from long unskippable dialogs which is fixed in these versions and the games made use of every hardware functionality in the 3DS, highly recommend these games!
Pokémon Series
The 3DS got a lot of releases and alternate releases such as Omega Ruby and Alpha Sapphire. My favorite being X and Y, featuring the 3D in most situations of the game! It also features a lot spinoff games like the DS. My favorite game being Y where you can interact so closely with your Pokémon!
Fire Emblem Series
The 3DS and the Switch features the largest catalog of Fire Emblem games at this moment. The best FE games you can get for this device are Awakening and Fates (get the limited edition with the 3 stories if you can!) which feature some serious high level of story telling that will more then definitely want to you discover more about the characters backgrounds!