I think it all depends on how the companies that own the rights to the shows treat them. I find most TV shows on DVD to be of excellent quality. 20th Century Fox has done a really good job on their older series' like Time Tunnel and Voyage To The Bottom Of The Sea, both look great. I've read that Mission: Impossible season 1 also looks great. I'm amazed at how good the picture quality is for Mickey Mouse Club serials like the Adventures of Spin & Marty and the Hardy Boys look, considering they were made in the 50's. New shows look amazing on DVD, especially Lost.

I have a few that are grainy, some episodes of the Munsters, Beauty and the Beast has a lot of grain throughout. I also don't like the transfer of the final set for the Adventures of Superman, throughout most of the episodes, the picture looks terrible for a minute, then good and then terrible again. That said, I love watching TV on DVD, most of the time the picture looks better than what I get on my satellite TV (DirecTV), plus I love the extras when Included and being able to see shows I can't normally see, when I want to.

Most of my TV shows on DVD are of the animated variety, and they often have a big problem with edge enhancement and noise in bright reds. I notice that a lot of British series (PAL or NTSC) often look very soft.

coolguy stop advertising that!
it's a BOOTLEG DVD selling shop

I saw 90210 Complete Collection DVD and I realized it because it is not released officially. only the first two seasons.

Not only that, many of the shows have not yet released beyond Season 2 or 3, let alone the complete series!