Mine was Samurai X aka Rurouni Kenshin. I did not exactly enjoyed the TV series right away until they released the series that told the story of how he got that X scar on his face.
To me personally, it depends on the series itself. Some anime like Inoyasha in my IMHO should be shorter. Fighting demons on almost every episode becomes repetitive that it becomes boring to watch. Sometimes I beg for them to just end the series to conclude the story already and move on to the next.