Cowboy Bebop, of course. Hito, why on earth would you ever consider Sailor Moon to be a higher quality anime than Cowboy Bebop?
...and now that Hitokiri is steamed I'll give you my major analysis.
Cowboy Bebop is a great anime, and so is Sailor Moon, but for very different reasons. Cowboy Bebop has style, quality animation, and great dialog, whereas Sailor Moon has some great drama, a good love story or two, and shelf life. Sailor Moon has about 8 times as many episodes as Cowboy Bebop, and while not everybody is a huge fan of Sailor Moon, it really does help to have that much story going for you. SM just has more to offer to those people who get addicted to it than Cowboy Bebep.
There are also the holes in Cowboy Bebop... I'm going to bring up a couple of things now that are spoilers, so don't read on if you don't want to lose that first-time magic (if you haven't seen Cowboy Bebop). [These are some serious spoilers people, do NOT read if you want to watch Cowboy Bebop all the way through.]
What happened to Ein and Ed after they left the Bebop in search for Ed's father? Actually, what the hell was the story behind her relationship with her father? Was there any story aside from the fact that he forgot her at a daycare because he's obviously a jerk. And what about Ein? What was his story? He was just some intelligent dog that was going to get sold at the beginning, and had no other purpose?
How about Faye's background? From what we can tell she used to go to high school. Wow. And she was in space when something happened to her ship and she was frozen as a result. Exciting. What happened? Where are her parents? We can assume dead, but can we really know? No. Why is that? Did they just run out of time for the series? Run out of funding?
Spike finally finds the woman he was searching for the entire series and she dies within what, an hour? Two hours? How anticlimactic! It should have been depressing, and it almost was, but it was too sudden and tasteless to move me very much. Same goes for Ed leaving and for Faye deciding that she had no place to return to. It was all too sudden and rushed to be as moving as it could have been had they worked on it longer, or pulled out a third season.
Lastly there was the ending. What happened to the syndicate? The Bebop? Why did Jet act the way he did about Spike at all on those last couple of episodes? Why did Faye turn around and start caring about him? Did Ed ever find her father?
Now I'm not saying those last few episodes weren't dramatic, because they were, but they have nothing on the real dramas out there, and Sailor Moon isn't an exception. Heh, to be honest though, I don't believe that Sailor Moon was really a better anime than Cowboy Bebop, I just think it had a few qualities that were stronger the same represented in Bebop. Cowboy Bebop was a great show, it just has a few holes, and it was too short for its own good.