Ignore mrpmpfan, he doesn't know what he's talking about:
Connecting your PS2 via component to your HDTV will allow your PS2 to show it's full potential.
Though PS2 doesn't pump out many pixels, only 480i though some games support 480p which can ONLY be reached with component-cables.
http://en.wikipedia.org/wiki/List_of_PlayStation_2_games_with_HD_support
Colour will be much nicer as the analogue signals are separated by colour so they don't blend into each other. Really, if you want to keep plying your PS2 then get component cables for a HDTV.
but it won't change the actual native resolution, MGS3 will still be rendered at only 480 vertical resolution which just is not all that much detail. But there will be less interference and could enable 480p which will make it look better.
Also to note: your HDTV may just have a terrible scaling algorithm (up from 480p to 720p or 1080p), that may be solved by switching to component cables.