I am a big fan of TV shows on DVD. There are a lot of series I didn't watch because I was busy doing other things (parenting stuff, community theater, living life with other humans instead of sitting in front of a screen). Now that my hip is in such bad shape, I can't do a lot of the things I used to do, so I am more inclined to waste time watching the tube. Watching shows on DVD is perfect because I can avoid commercials, and I can schedule the watching on my own time.
One series I recently purchased is Freaks & Geeks. I didn't catch this show not only because of NBCs capricious scheduling, but because when it was on the air I was involved in two different community theater productions, Three Short Plays by Christopher Durang and A Little Night Music. F&G was a great show, and the DVD is ridiculously abundant with delightful extras - there are commentaries on every episode, and you can feel the love that everyone associated with the show has towards their collaboration. It's a critically acclaimed show that many felt was cancelled too soon, but it's one absolutely perfect season, at least they never declined in quality.
Speaking of declining in quality, I spent much of the ridiculously cold weekend watching Buffy the Vampire Slayer, Season 2, on DVD. I didn't start watching this series until it was in its 4th season, so I had to buy the previous seasons to catch up. Season 1 was okay, but Season 2 and 3 were mostly fantastic (On the plus side: Surprise, Innocence, Passion, Becoming Parts I and II. On the minus side: Inca Mummy Girl, Bad Eggs, Go Fish (seriously, what were they thinking?). Unlike a lot of fans, I really enjoyed the show until the tail end of Season 6 - I confess, I really liked Buffy & Spike together, so I was only disturbed by the ridiculous magic=drugs storyline they gave Willow. I probably won't even bother buying Season 7, because it was like a different show completely.
Angel was on a different track than Buffy entirely. I think it started slow and picked up steam, and each season was on the whole better than the season before it.
But here is where I commit heresy: Firefly was, in my opinion, the best of Joss Whedon's creations. I know, Buffy's an icon, Angel's cool, but Firefly was so much more complex than either of these shows. Buffy and Angel both touched on the gray area between good and bad, but Firefly lived in the gray. I think the show had the best acting, the best sets, and the most potential of the shows Joss Whedon created. Of course, it's easy to talk about the potential of Firefly when it was cancelled halfway through the first season. I actually shed tears when I heard it was cancelled. I am trying to not get too excited about the movie, Serenity, so my expectations don't get out of control. I will be there on opening night, though.
My only complaint about TV on DVD is that some shows I would like to watch again are too damn expensive. X Files, Six Feet Under - I'm looking at you.