I'm really into TV Series these days, since some of those series really beat the crap out of what's in the movie theatres.
I just ordered the first 4 volumes of "Smallville" from Amazon. Pretty cool series, especially if you're between 15-25. Shark was also pretty cool, but it got cancelled.
Some of my favorites would definetely be House, Bones, Boston Legal, NCIS and CSI (only Vegas though). I'm also a great fan of J.J. Abrams' work and count Alias and Lost to my all-time favorites and am looking forward to his new series, Fringe. I used to watch Numb3rs, but it got a little farfetched in my opinion. The Sarah Connor Chronicles are great and so was The 4400 (which was cancelled). I'm already looking forward to see 24, Heroes and Life again this fall.
I haven't seen that many older series (guess that's due to my young age
). Magnum P.I is definetely worth checking out, though and you also should have seen The Young Indiana Jones Chronicles. Last, but not least, I'd like to recommend a very special favorite of mine, Rome. If you're over 16 and you don't have any problems with violence and frequent nudity, you should really see it.