I am running emulation station on Retro Pie. i've seen this issue posted maybe 5 times, never with an answer.
when i'm in HDMI: i get the game rom select screen, i press the button for accept, it goes to a terminal and some codde streams by- then it loads the game full screen (it works on most emulators and roms i try, just don't have some drivers or something for game boy etc. but it does work and well)
when i'm in component: I get the standard game select screen, accept a game, get terminal, then instead of the usuall code i get many lines of "=======================" across the screen, at which point (maybe a second or so later) it goes back to the game select screen.
my only guess is that the emulation station favors high definition and isn't happy with low res, keeping you from booting a game.
or perhaps the game does run but is immediately pushed to the background?
i make this thread because nobody has made a fix yet (from what i've seen) so if anybody does know it hopefully this can be a definitive fix. I'll post again on the retro pie forums if they have one- ill look around.