I can't really do a top 5 list, haven't really bothered with TV much since I went to university and lived almost completely without it for a few years.
The only things I really watch now are police things - Police Interceptors, Road Wars, Cops With Cameras, etc - and Top Gear. Then there's the things I watch on DVD, which is mainly American shows that I always miss when they're shown on TV: House (pretty much my favourite show ever), CSI (original and NY, not Miami), NCIS, 30 Rock, Boardwalk Empire, etc.