I've been an anime fan since 2004. I like all types: seinen, shounen, shoujo, comedy, mecha, experimental, etc. In general, I prefer dubs if the dub is good =O. I think it provides a more immersive experience. However, at this point, I tend to choose how I watch on a series-by-series basis. In my ratings, I take into account all characteristics including animation, music, creativity, character development, plot, and also just a fun factor. However, I give high marks for shows that do something better than any other show. With all that in mind, I think Cowboy Bebop is the best anime series ever created.
2012 Update: Bebop is still the greatest.
2014 Update: Bebop STILL the greatest. Yep, still. In the past year, based on my personal convention experiences, I can add the following. Shinichiro Watanabe is the coolest guy ever. Yoko Kanno is the most adorable person on earth and unfathomably talented. The Bebop American voice cast is hilarious and awesome, especially when they're all together in one place.
Also, find and watch Legend of the Galactic Heroes. Every bit of it. It's as brilliant as everyone says it is. Score: 11 out of 10.