i would recommend Bladestorm - probably the best Koei game this gen and one of the best hack & slash from Koei you should pick it up for 10-15$.
Dynasty Warriors Strikeforce is great too - great mix of strategy and hack & slash.
if you have psp pick up Warriors Orochi 2.
i wouldn't bother with anything else from Warriors series this gen(maybe except Dynasty Warriors: Gundam 2 but only if you're a fan of the Gundam franchise).