With no preconceived intentions I've been putting a lot of time into 2D side scrolling shooters lately, trying to complete Contra 4 (NDS), Commando: Steel Disaster (NDS) and the original Megaman for NES.

They're all very difficult.

I guess that's the whole idea though, at the core of most 2D shooters no matter how well designed is a limited amount of gameplay content. The hours of play you gain from a purchase are in trying over, over and over again - perfecting your skills.

Then again most modern games such as the above DS titles incorporate a form of saving progress so once I get through a few last levels I'm wondering how long they really will last.