It’s still a great little system. It has a large library with a lot of great games (like you said), but also quite a bit of shovelware. The phat and Lite models have backwards compatibility with Game Boy Advance via Slot-2 and a few DS games can interact with the cartridge in Slot-2. There’s also the DSi models which sacrificed the second slot for better hardware and new functionality. The DSi has a few exclusive titles that don’t work on the originals.

There’s also a lot of cool homebrew for the DS family. For phat or Lite models you’ll need a flashcart (I recommend a DSpico as the hardware and software are fully open source). With a DSi it’s possible to softmod the system to run homebrew right off the system SD card.

An important thing to know is that the hinge is a bit of an Achilles’s heel for the system. The plastic of the shell is prone to becoming brittle or even disintegrating over time. Regardless of which model you pick it’s a pain to replace the shell. Additionally, only the Lite has high quality replacement shells available, so if you have a phat, DSi, or DSi XL then you’re kinda out of luck.

I’d suggest 3ds if you have access to that, then you gain access to almost all nintendo’s handheld games except switch. It’s very easy to hack too from my experience 2 days ago.