Many people have ratings systems for how they will rate anime, my system is more based on general enjoyment rather than particular separate elements such as; visual, story, charachters... etc.
With that said; Interesting Characters, Origionality, and Storyline trump all other elements. For example, you will note that One Piece is "5 stars" because though it has some boring arcs that are a bit too long, its extremely origional storyline and characters forgive any other anime misdeeds it could ever commit. There is no way to ruin that show.
I don't care about the type of anime as much as I do the enjoyment it brings. I generally prefer adventurous anime, fantasy, and comedy.
Another key to my ratings is Mystery. Mystery is a wild card in my ratings. Some Captain Harlock, Hunter X Hunter, Ghost in the Shell, Attack on Titan... have this elusive element.
Most Entertaining: Hunter X Hunter, Ghost in the Shell, One Piece, Bebop, Paranoia Agent, Gurren Lagan, Trigun, and anything Miyazaki...