I consider Buffy, Angel and Farscape to be my Holy Trinity of TV. Buffy is my favorite series ever, but it would be a bigger investment, as it is 7 seasons and it has a spinoff that lasts 5 (and part of it should be watched concurrently with Buffy). Farscape is amazing too though, easily my favorite sci-fi series. It is creative, out there, and has some wonderfully developed characters. Both shows take a bit to find their legs. For Farscape it is towards the end of the first season, for Buffy more towards the middle of the second. But all the shows are great and worth watching.