Hellsing
I like Ultimate, and the first anime, but Ultimate is overall better.
Berserk
The only thing I hated about the anime and movies was how they were both pretty much a prequel to the main events of the manga, so glad they're finally gonna continue though
EDIT: I can't believe I forgot Dragon Ball Z
And the first anime I ever watched was Dragon Ball Z
I use to watch Inuyasha when I was younger, I've seen the ending, but there's quite a few episodes in-between that I've missed
Then there's Digimon
Digimon was my favorite show as a kid, and I heard they were bringing back the original cast for a new series (a series of movies, but still a series) and I saw the first one, and it was just pure nostalgia.
And they're not really long running animated series-es (Plural for series, anyone?) but also enjoyed the Devil May Cry anime, and I did see a couple of the Marvel animated series-es, and personally I liked the Blade one the best, could be biased though. Blade's my favorite underrated comic book character