I'm normally not a fan of 'long' series, but here's a few I enjoyed:
Dragon Ball
->Maybe the first arc of Z, but after a while I got REALLY sick of Z
Crest/Banner of the Stars
->1 season for Crest, 2 seasons for Banner plus 1 OVA, and there's two or three movies
Soul Eater
->One of the few 'over 50' episode series I like
Clannad+After Story
-The feels, o dear, them feels
Mobile Suit Gundam
->Big fan of the short series 08th MS Team
->MSG: 0079 is a classic
->Gundam Wing is 'modern classic'
->Gundam 00 was pretty good, minus the retarded movie
->Turn-A Gundam is just...AMAZING, and that's before you factor in the OST by Yoko Kanno
Galaxy Express 999
->Over 100 episodes, but for some reason I REALLY enjoyed it
Blood+
->Overall not a bad series, WAY better than Blood-C
Eureka Seven
->Great series, if a bit weak in the middle
Ronin Warriors
->Power Rangers in armor
Ghost in the Shell: Stand Alone Complex
->Great series, just pretend the 3rd 'season' OVA never happened and you'll be fine.