Chuck- Really liked the show when it first came out. The girl I was just in love with from the first episode. And then she was on Dexter which just made it icing on the cake for me.
Spartacus- With the death of the origional actor, I really lost interest in the show.
Voyagers- Not sure if anyone remembers this show. It is what Quantum Leap (great show!) was based off of. The main actor died after the first season, so they didn't renew the show. Was really good though.
Lost- After about the 8th episode when they kept throwing hints out there but NEVER FETHING ANSWERING A SINGLE THING, I walked away.
Heros- See above.
Las Vegas- I agree, after Ed left, the show just went to crap
Air Wolf- That helicopter was pure badass! They got 2 or 3 seasons in and then the one guy went to prison for beating his wife. That just killed it right there, never renewed.