NES: Zelda the original
SNES: Street Fighter, Super Battleship, Super Mario All Versions (one rom), Teenage Mutant Ninja Turtles (i know you played this in the arcade), Contra
SEGA: Golden Axe 3
PSP RADIO: Heard it works for some and not others on 2.6 (kinda cool but i really dont wanna just listen to my radio, its be a lot cooler if i could surf the net at the same time...)
APPS: None really

LUA is kinda awakward for me crashes a lot...
All the DOOM WADS seem cool like counterstrike and what not but need a bigger memory stick I believe..
Truthfully I have more fun PLAYING with homebrew then actually having a use for it... Been thinking about upgrading but I know when I do they'll come out with a downgrader the day after for my 2.01 : / ..
Only thing I really want is to use the OS skins and UMD replicator thing..
IMO no homebrew game can touch any actual psp game (2.01+).. N64 would be way cool but hes having a hard ass time programming that...
Hope this answered some of your questions.. I have all those games I listed above and while fun to recreate some of your child hood memorys honestly it gets old wayyy fast.. Just my two cents...