One of the more under-rated actors of our generation. He hasn't had the big "A-class" movies - but this is probably only due to the fact that everybody will always see him as Jack Bauer of 24, and will struggle to see him play anything else. He is so good as Jack Bauer, that he has single-handed made the show one of the best on television.
When it comes to TV characters tough men, Jack Bauer is always included (along with the likes of Bourne or Chuck Norris :)) - and this can only give credit to Kiefer's outstanding acting abilities.
I hope that he gets given a break on a big budget movie, so that non-24 fans (are there any out there?) will see his qualities as an actor.