neo drift out (top down racer) should play a bit overclocked doh or the sound is not that great.
wonderboy (jump n run) series plays good on standard setting
1942 (good shooter)although it's a bit hard playing with the joystick imo
commando (us/world) (action) plays ok but again hard with the gp2x joystick
arkanoid (world) (breakout) plays ok with the joystick & default settings it's the mother of all breakout games
galaga (shooter) plays good but i need to stretch the screen in order to see my plane
galaxian (shooter) plays good but i need to stretch the screen in order to see my plane
ghost n goblins (jump & run) plays good
gyruss (shooter) plays good
Kung fu Master (action fighter) good old kung fu master anyone should have played this
can be a bit hard with the joystick sometimes
pac man
plays ok
snow bros (kind of puzzler) plays ok
there are plenty of others as well to much to name u could use MAWS (google it) to look up the games u actually want it has screenshots as well as information and u can look up games by genre. one note doh maws list games of the latest romset so not all games in maws are in mamegp2x