I really love DOA... first off, Hayabusa is there!
That guy is my hero, I wish they'd kept his original costume.
The gamplay is complex, yet it is very easy to learn, though not so to master. Especially on DOA3, where the environment can be actively used...(jumping and running up walls, etc...)
Third, the counter system makes trhe fights look more realistic and makes people think twice about throwing the longest combos several times...
Fourth, its a fluid game, kind of like soulcalibur, my other fighting favourite... I hate the stiffness in the moves from tekken and Virtua fighter.
And the Ladies!! Don't forget the bouncy ladies!!!
(did you guys hear about the "topless" cheat in DOAX?)