I have a Samsung Series 5 46" LCD Tv which I purchased back in 2009, it was HORRIBLE, after just one year (conveniently, just around the time when my warranty expired), the TV started showing display problems just then, half of the screen would go black & keep flickering for sometime. I called the service center guy & they told me it would need a panel replacement. Apart from that they have crappy build quality for their power board, which in my case had a capacitor blown once as well.
Mind you I am not an isolated incident, my brother also got a Samsung 32" Series 4 LCD from Dubai & that had the same display problem on Day 1 (luckily he got it replaced).
I have never owned a Sony Tv, but my friends do & none of them had any problems with theirs since the last 5 years or so. So I would recommend Sony.
No idea about LG though.