I'm the same way. I prefer to play co-op with my friends in-person, as opposed to online. Sometimes my roommate will just split the screen on his bigscreen TV and we'll each play something different. All I know is I need to find a way to get out of my single-player funk and start playing some RPGs or something.
I actually played the original Ninja Gaiden a couple weeks ago. Trying to finally finish it. Suffice to say I got a bit aggravated and turned it off. That damn last boss.
