OKAY SO THIS IS WHAT I DID
First, I'd just like to say this worked with my XBOX games, not 360 titles. I did not try the 360 titles.
Went to Memory, and found the games. For me, it was Scarface and KOTOR. Deleted EVERYTHING about them. It was probably just the game saves anyway. After deleting everything, I "recovered my gamertag." Just filled out the exact same information, downloaded my gamertag, and bam. Kotor and Scarface were removed from my games. No achievements, not even in my listing of games. Totemball is still there I believe.
So, it worked with XBOX titles, not the 360 one. But I'll try more stuff to see if it works. :-)
If the previous posters were talking about the 360 titles, then I guess you're right. But to the others, you CAN get rid of XBOX original titles. Sorry to the people trying to remove 360 games. I'm still trying.