StarFox, Resident Evil Revelations, and the Etrian Odyssey games have been my favorite 3DS titles. For DS compatibility I really enjoyed Dragon Quest IX, GTA Chinatown Wars, Contra, Castlevania, Megaman Zero Collection, and WarioWare DIY. My taste in games is weird, so take these recommendations with a grain of salt.
My purchases over the past couple of weeks:
* Lego Batman 2 (Wii) - One of the last Wii games I wanted to add to my collection, finally found a very cheap copy online.
* Scribblenauts Unlimited (Wii U) - Paid "too much" at $20, but really wanted to play this with my kids. The DC Heroes version had been on sale for half that price, but seeing my son laugh as we put Mario and Boos through their paces is worth the extra expense.
* Dungeons & Dragons: Chronicles of Mystara (Wii U) - Wish there was a physical release, but pretty happy with this otherwise and can understand why this is digital only. Not a huge fan of beat'em up games but the RPG elements really make this one shine.
* XType Plus (Wii U) - Wow, this is really enjoyable in short bursts. Highly recommended.
* Kirby Super Star (Wii U VC) - Club Nintendo reward.
* Super Punch-Out!! (Wii VC) - Club Nintendo reward.
* GTA: Vice City Stories (PSP) - Kind of like having a stacked PSP Go ready to take with me anywhere. For $2.50 I'll bite on some portable GTA.
* Xenogears (PSOne Classic) - Sadly, bought just because I'm curious about the weak Xenoblade connection and because I was adding funds to my PSN account anyway for GTA (above).
* Humble Indie Bundle 12 (Steam) - So less than $8 for Gone Home, SteamWorld Dig, Hammerwatch, Gunpoint, LUFTRAUSERS, and Papers Please... with more to come later? Sure, I can bite on that. After this gen I'm planning to bow out of consoles anyway and go for the cheapest Steambox that will play most of the games I already own. At that point all I'll need is to win the lottery, retire, and finally have time to play all these games.
Edit: Wow. Didn't realize how much I bought until looking at the list - that's like $50 wasted on games this month. Stressed at work, and taking it out on my wallet. Oh well. At least they've got good company in my backlog.