Ninja Gaiden is freakin' awesome. It takes like a day just to beat some souped up heavily armored machine crazy helicopter!
I'm on a Ratchet and Clank 2 craze right now. I can't get enough of it. It may be only a "platform" game, but it seriously has everything. There are parts where you hack and slash, fight in your spaceship, grind down railings, hang-glide, snipe enemies, and you build up your life and your weapons as you go on...just like an RPG. I highly recommend this game, the replay value is incredible.