For some reason, I never had luck playing MGS on a PS2, I tried it on 3 PS2's !! (My old fat PS2, my friend's slim PS2, and a slim ps2 that I recently bought!). It just wouldn't load on a PS2, it works fine on a PS1 or PS3.
I have had some issues playing PS1 games on the PS2 using component, and I know I'm not the only one. LCDs tend to exhibit the issue the most - someone claimed it was because PS1 output was in 240p instead of 480i, and most TVs can't handle 240p, but I really don't know.