1.) Great Love story triangle <Ranma 1/2, Naruto, FMP...etc>
2.) Good animation
3.) Fighting scenes
4.) Unpredictable twist <but nothing too crazy that you lose point of the story>
5.) Last a couple of seasons
I think with all that....one would have a great series for me.
Ranma1/2; Full Metal Panic; Robotech; Full Metal Alchemist; Fate: Stay/night