All are definitely worth watching, think I was the same with 24, only really started watching it last year and got hooked! It's REALLY addictive! Now my wee brother is into it, and has watched the first two seasons in 2 weeks!!

Heroes is class as well, really good story lines in the first season, but yet to get going in the second!

Lost is good too, but can be a bit confusing and some episodes just dont seem to go anywhere!!

As mentioned above, Prison Break is also good, back on track after what I thought was a poor second series!