All my friends have played Cave Story. Even girls play Cave Story at my university. My Computer Science professor AND my former Linear Algebra prof have both played Cave Story. The manager of the Residence Halls has played Cave Story. I'm pretty sure the cafeteria lady also played Cave Story like once or twice. She always got the machinegun. My sister has played Cave Story, and she never gets anything. On purpose. She just goes through Sacred Grounds using the Polar Star and beats it in about 3 minutes 40 seconds. She can do a 3hp run of Sacred Grounds in about 5 minutes. And she's 14. I can't even do that.
You guys have really bad friends. Almost everyone I know, including my parents, siblings, close friends, and a handful of staff + professors at my university. They have all played Cave Story. Almost all of them could whoop your ass in Wind Fortress for CS+.
How did I find out about Cave Story? All my friends played it first, and THEN they told me, "hey you should check out Cave Story. It's free and it's a good game". I was the last of my friends to know about Cave Story - Doukutsu Monogatari.