I am a devoted fan of Buffy the Vampire Slayer. That is probably the only show I've ever really been hooked on. I loved the writing because the show was always exploring new angles to keep the ideas fresh. The characters evolved beautifully from the beginning to the end of the series, like how our dear Jack Twist sadly lost a lot of his adorable hope as he grew older (okay, I just HAD to throw in a BBM reference), and the actors were very consistent and authentic with the parts. Plus, it makes me laugh aloud, cry, and it keeps me thoroughly entertained. P.S. Joss Whedon is a very good director (See: "The Body," "Restless," "Once More, With Feeling").
Aside from that, I like The Simpsons, Daria, and Reba a lot. Predictably, I like Angel but I've only seen a handful of episodes. Ghost Whisperer, Family Guy, Friends, Will & Grace (early years), and Smallville are enjoyable but I do not keep up with them because they all frustrate me from time to time. (Actually, I did keep up with Friends; though very over-the-top, that show was pretty good.) I've been especially bad about keeping up with these since I saw Brokeback; for weeks, I virtually stopped watching television because of my love of Brokeback (it's hard to watch something supremely inferior to BBM and think of Jack and Ennis the entire time).
Veronica Mars is a good show as well. I've only caught a few episodes but Kristen Bell is a solid actress and really works her part well.