I started off watching One Piece because i was getting sick of waiting for the next Naruto Shippuuden or Bleach to be released, an after about 30 episodes i was hooked! Excellent Battles, Unique animation style, Story line to cry to lol.
I couldn't believe this was the same program i had seen on toonami years ago, which is pap in comparison to the original, don't watch dub ever.
It's also the only long running anime iv seen to break away from the usual anime story suspects like :- Mecha, Ninja/Samurai, Sport and themed shows.
Which IMO makes it the most likely to be immortalized more so than Naruto or Bleach, there is a reason why even Toriyama (the DB creator) heralds One Piece with being the DBZ, and that reason is pure win.
One Piece is without doubt my favorite long running anime, and possibly tied for number one spot with Deathnote for all anime, ever.