are they similar or

I haven't seen the original in maybe 10 years... From my recollection, it's the same story till about halfway through. The first two episodes of ultimate I know are pretty much like the show (with the Valentine bros part being the second ep in the ultimate series). The third episode I think things start to steer away from the show and by the 4th episode it's completely new ground.

From what I understand, the Ultimate series more closely follows the comic from which it's based while the original tv series deviated and made up their own story past a certain point.

I honestly don't remember how the original series ended but it certainly wasn't the way ultimate did. I liked the show but I wasn't super stoked about it. The ultimate series is way better... I just finished watching that tonight after owning the first 4 parts back when I was in my anime phase... Decided to finish the series after discovered they finally completed and I can't say I was disappointed. I thought it was bloody great (pun intended).

If you liked the original, you'll like this no doubt. The artwork is better even though it was great in the show too... But this obviously had a higher budget.

In the original series, there is no mention of nazis, but they are the main villain in ultimate.