Monster Hunter 3 Ultimate! I just recently got Citra emulator running on my steam deck and it runs great. Plus, Citra can emulate local multiplayer over the internet, so I’m playing with my old buddy who moved to california. Just like we did back in our highschool days.
I have no clue about the old launcher, but the current launcher allows you to select any version all the way back past alpha. It was a lot of fun to try to hunt down which version I probably first played.