LCD TV - Blurry picture on many large sets ?

Turning to this forum to try to get an answer to a problem i've seen on many large (>37') lcd and some plasma sets. I've read through the reviews on THG but never seen an answer to the following:

If you look at a film with rapid horizontal movements and the picture consist of vertikal objects (like buildings, trees or people standing) you will see that the objects are moving with large jumps and not as smooth as you would expect comparing with a CRT. The picture sometimes get so blurry that it ruins the whole experience. A salesman once explained that it mostly was due to bad input signal power, but i honestly don't belive that's the only explanation. This symptom can be seen on many larger sets. On smaller sets this is not as obvious.

Is it an intepolation issue only or can one expect that cheap (?) $2500 sets simply is lacking the appropriate processing power....or is it a combination ?

Btw: Analog input seem to be the worst scenario in this aspect.

/S