an LCD = crap in crap out.
some are more friendly but 90% will give you a crisp bright PC picture but a god awful freeview, SD image
the sammy of mine took ages to sort out an exceptional picture (not just an average one) its horrid at low res stuff, but on 720p, 1080p/i its stunning, not for the colours or definition but for the fact its the first LCD ive seen with plasma rivaling blacks and no image lag i.e great for games.
http://www.hdtvtest.co.uk/Samsung-LE40M86BD/
^^^
here is an exellent full review.
look at it like high end audio equipment, play mp3 through it and it will sound flat, 2d, you will hear the phasing sound and compression artifacts, but supply it with a top end cd player or vynil recording and it will blow you away.
plasma is a lower res alternative for the masses to watch there with there junk equipment.
and im talking £800 40" lcd vs £800 plasma not a £6k plasma because they are obviously awesome however even at £6k you will struggle to find a decent 1080p plasma with 3 HDMI inputs like the sammy 40"