If you do want to see an american film on similar subject matter which really is kickass, Inglorious Bastards is damn awesome - and I've had German friends commenting on how the language flips from english to french to german - by a german actor playing an SS officer - really worked well - Didn't expect much as the last few tarantino flicks weren't all that, but was really pleasantly surprised...
I enjoyed it too, nice revenge fantasy. I'll put Der Untergang in the queue.