Mira: Haha, I had to say Top 3 because well I couldn't narrow it down to 1... :)
1. Jack & Jill (1999-2001): I'm a major shipper as is apparent on this blog. In any case, I loooooved Jack and Jill and was really pissed off how the show didn't allow them to end up together after Season 1. Then got canceled after Season 2, which had ended on a cliffhanger! I've never gotten the resolution I so desperately wanted... For those who don't know the show, it's about a guy, David Jillefsky, called "Jill" and a girl, Jacqueline Barrett, called "Jack." Starring Amanda Peet, Ivan Sergei, Sarah Paulson, Jaime Pressley, Simon Rex.Jennifer: I totally agree with Jack & Jill above, but here are a few more of mine.
2. Studio 60 on the Sunset Strip (2006-2007): Funny because this show also starred Amanda Peet and Sarah Paulson. In any case, this show started at the same time as 30 Rock and had a similar premise -- backstage of a weekend variety show similar to SNL. 30 Rock was all comedy; Studio 60 was mostly drama, West Wing-style. I looooved how Matthew Perry and Bradley Whitford played off of each other. I loved rooting for Matthew Perry and Sarah Paulson to get together. I liked Amanda Peet as the person in charge... But it tanked. And didn't even finish airing!
3. Gilmore Girls (2000-2007): This doesn't fully fit the category. The real problem with this show is that it was dragged out too long. So long that they had to ruin the perfect couple: Luke & Loralie! Then because it was dragged out, it was kind of abruptly ended at Season 7. The two sort of got back together before the end but not to the extent that I needed. I had 7 seasons invested in this relationship -- they should have been married with twins (a dream Loralie had in an earlier season) by the end! Not rebuilding a broken relationship. GRR!
1. Firefly (2002): Yes, I'm a Joss Whedon fangirl. I fully realize that most of his shows are pretty out there and just don't have a wide enough appeal to get the ratings needed to survive on network TV, but Fox really didn't treat this well at all and its premature cancellation really hurt. I loved the space western concept, and the crazy slang and cursing in Chinese, and it had that trademark Joss Whedon combination of humor and heart. The cast was just phenomenal (launching the careers of Nathan Fillion and Adam Baldwin and Summer Glau) and every single character was really memorable and well-developed. The consolation of course, is that somehow Joss got to make a feature film, Serenity, which was generally self-contained but in a way wrapped up some of the storylines from the series. But the series just had so much potential and I'm still sad that we only got one season out of it.I'm going to cheat on the question and mention a few more. It seems I like to collect DVD sets of these kinds of "brilliant but canceled" shows...
2. Kyle XY (2006-2009): I think one of the reasons I loved this show so much was that it reminded me of shows like Roswell and Dark Angel that weren't on the air anymore. But it definitely had plenty of its own merits too. Matt Dallas was so great portraying Kyle as he gradually learned both the good and bad of being human, and I actually loved when they introduced Jessi as Kyle's counterpart who wasn't so lucky. The Tragers really grew on me, and I even ended up loving Hillary. Of course Nicholas Lea was awesome as Kyle's mysterious protector, Foss, and I also loved the hints that Declan was kind of being groomed to take Foss' place. All the Zzyzx and Latnok stuff was sometimes kind of silly and ridiculous but things were actually going to an interesting place at the end of the third season when it was abruptly canceled. Also I was a big Declan/Lori shipper and I'm sad that their story wasn't really resolved. Evidently the third season DVD has a featurette discussing what the plan was for the rest of the series. I really need to buy all the sets!
3. The Middleman (2008): Another case of something being a little too out there. This was based on a comic book series, and was about a very straight-laced crimefighter/superhero called the Middleman, and his artsy, unflappable sidekick/apprentice, Wendy Watson. Together they fought generally wacky evil beings, like mad scientists and aliens and things of that nature. The show definitely embraced its kookiness and was just a lot of fun. It's unfortunate that it was canceled after just one season while that other ABC Family show that premiered the same summer (The Secret Life of the American Teenager) went on to become kind of a huge hit.
4. Wonderfalls (2004): In a way, I'm ok with this only having had one season. (13 episodes were filmed and are in the DVD set but only 4 aired.) I read some ideas that Bryan Fuller had for the second season and they were pretty wild and I'm sure it would have been fun, but I think that just the one season is just pretty perfect and Jaye and Eric ended up together so I'm happy.
5. Kitchen Confidential (2005): Supposedly based on the book by Anthony Bourdain but it really just went in its own direction and was hilarious. On the surface, it was really just a variation on the workplace comedy, but I thought the kitchen setting was fresh and funny. Bradley Cooper did what he does best (be charming) and the supporting cast was hilarious, with Owain Yeoman and Nicholas Brendon and John Francis Daley and John Cho and even Bonnie Somerville. Another Fox casualty that canceled was after only 4 episodes (all 13 are also on DVD). Man, Fox really sucks...
6. Grosse Pointe (2000-2001): A 90210 parody, I was just upset that Marcy and Dave the Stand-In never got together.