If you haven't seen them, Lost
's not sci fi but it doesn't matter when something's that good.
varies in quality but the characters are great and when it's good, it's really good.
is a lot of fun. S1 is great. It's a bit more boring in S2 and now in S3 it's back to being very fun but is getting really incoherent and the characters are dumber than ever. Check it out anyway, if the characters grab you, the flaws won't seem so important.
Delving into more non-sci-fi series - Big Love, Entourage
are worth checking out. Entourage
takes a a bit to get going, S1 isn't its best. The other two, either you'll like them from the first episode or don't bother with the rest.