the 3ds has an amazing library of games, not to mention it's backwards compatible with ds games as well. hacking it is the easiest way to get games for it since the eshop is down, not to mention the extra benefits like custom themes and homebrew applications and whatnot.
my personal recommendations depend on what kind of games you like, but my favorites are definitely 3ds) the persona q games, project mirai dx, pokemon sun/moon and ds) rhythm paradise, pokemon black/white 1+2, sonic rush and warioware diy. i'd also recommend bringing your 3ds to places like conventions because people there tend to bring their 3dses as well and you'll rack up streetpasses for extra features.
if you have a homebrewed 3ds, you can get twilight menu to play ds roms without needing cartridges, and i believe the other emulator launching capabilities it has require installing emulators to launch with since i haven't gotten them to work natively. google is your friend.