Hi Guys,
Sorry for the delayed response as I was preoccupied with stuff.
Now coming to the point,with reference to Nishant I certainly beg to differ to his views on dvd quality on composite video and compression of MPEG4 being better then MPEG2.
MPEG4 is high compression format where the video quality is not completely restored when decompressed ( same way as the MP3) where as the MPEG2 is "THE" video standard for so many formats and it is a encoding and compression format where the quality is the atmost important then anything else which is only comparable to uncompressed AVI format, so in no means or way can you compare MPEG4 to MPEG2,it would be comparing cd sound to MP3( hope now some one does not say that MP3 is better then CD

)
now talking about the dvd quality picture on composite video,if that were the case then they didn't have to invent component and progressive scan and now HDMI with 1080p they would've stuck to plain old vanilla composite.the thing with composite video is all the data i,e chroma lumninence and brightness are mixed and sent and the video section in the TV where all these is segmented and sent to the respective stages for further processing before being displayed.in component its not the case with other types, all the video data is pre split in the form of Y,Pb,Pr (chroma,luminence,brightness) so there is no need for the same to be done in the TV,so the signal directly goes for processing and displayed hence the better quality of picture.Most of the DVD players the video section itself has separate DAC's ranging from 54Mhz to 208Mhz and from 8 Bits to 14 Bits so comparing all these with the plain old composite is how far debatable is left on the one's understanding of the subject.
Another thing that Nishant mentioned is compression levels that each uses for their own channels,again I dun know how thats true as I have the dishtv for over an year now and I can vouch for the fact that Zee Tv in dishtv is no better then star on the same,the real difference in the picture quality that I have noticed is in the foreign channels (ex: DWTV,TV5 Asia Etc) where even in the composite you can easily make out the quality difference.
Now coming to the sat questions:
1. Whether our eyes can feel or see the difference between so called Tata Sky quality and a DVD quality? when we are viewing from a costant distance.
Yes you can 100%
2. Quality of pictures will also depend on what type of TV you have i.e. a CRT or a plasma?
Yes true you right but not entirely,you see more then plasma TV CRT and LCD it depends on what the spec of that TV is irrespective of the type to judge the quality, for example an 100Hz progressive scan CRT will any day outperform any regular plasma or LCD .in fact I still prefer CRT for viewing then plasma and LCD for Obvious reasons, this in itself is separate topic which I don't want mix it here

.
Hope I have shed some light on this topic with the above information and hope I have not offended any one in the process,if so please excuse me as my intension is not that.I am just trying to share the details of the technology.
Regards,