Babylon 5 is truly legendary...and lets not forget that there is another sci-fi series that has had a huge appraisal all over the world. Also a bit old:
SG-1, Atlantis and Universe all of them are good.
Also L.A Law was a great show
[Edited by benduhova, 5/4/2012 5:04:01 PM]
Exciting, though? Traditionalist (read: warmonger American) excitement might be found with Band of Brothers and Generation Kill. Though the latter is more funny than action, in that quirky guys-who-shoot-people way. Both are miniseries, so technicalities (they had one season each and were on TV!) mean they are relevant to thread.