As someone who only played 1 and 2, this feels like a downgrade to me
The first two games had this almost unexplainable fluidity and cohesion to the combat that just isn't here. The way punches and kicks would transition into grapples and counter attacks just felt so organic, and you didn't need to be a pro at the game to feel like a master of martial arts. But here that magic is gone. DOA5 feels much closer to Tekken or something.
Though of course, unlike Tekken, there's not much to do here in single-player once you beat the story, which I didn't. In the first two games the story was very minimalist with practically skeletal cutscenes, and that was fine. The cutscenes added a flair to the game, but didn't overstay their welcome. Everybody understood that it was all about the fights. Here cutscenes really drag on, and it's not like the quality of writing has improved or anything. From what I played every single cutscene was totally skippable. Most of them were literally about nothing.
Also I feel like this game is more overtly perverted than the first two. Like sure, you had skimpy outfits and booba physics, but that was it. The old games almost feel kinda like innocent mischief. Here you can turn off the booba physics, but I feel like everything here kinda rubs sexiness in your face. There's literally a found-footage-style cutscene that's just one of the characters entering her locker room, getting really close to the camera with her sweaty body, then leaving to take a shower and then coming back to the camera and saying like "oh, I forgot to turn it off" lmao. That's the entire cutscene! What is the point??! And then there's little things like, when your character is defeated, she's just kinda lying on the ground and moaning, which I found suggestively erotic. But hey maybe that's just me with my dirty old dog mind.
I'm also not a big fan of the visual shift from the colorful Y2K aesthetic to a more realistic look.
But honestly, technologically the graphics are kinda amazing for Vita. Like, there are pre-rendered cutscenes from like the PS3 version I guess, and then when it transitions to the gameplay, you almost don't see any difference. It's crazy. Compare this to, say, Mortal Kombat or Injustice, which both look worse and perform worse on Vita.
All in all, I think DOA5 is a solid game, but I don't see much reason to play it over the first two. I mean, I guess if you're a fan of the series, it's nice to have a DOA on-the-go, but I don't really care. I'd love to have a Tekken game on Vita. But we can always just play Dark Resurrection or the PSP version of Tekken 6, I guess.