Right I tested the US version of the game Alien Trilogy on the PSX. I used both emulators (even though they both say they've been ported from the GCW0) and the triangle button was working. (Got to the point where I picked up a shotgun and was able to switch between it and my pistol with the triangle button (X button on the RS-97).
Don't know if it's relevant but I was able to start the game by either selecting the cue or bin file.