See, the problem is, people confuse "100 Marios" with Super Mario 128:
100 Marios: A tech demo of a bunch of Marios running around, used at E3, etc. to demonstrate the GCN's power. Later became the engine for Pikmin, basically.
(Super) Mario 128: With 128 being the natural progression of the GCN's power from the N64 and so far back in time (8-bit, 16-bit, 32-bit on occasion, 64-bit...), this was the code-name of sorts for an oft-promised, never-released Mario game on the GCN to follow up Super Mario Sunshine. For all we know, Super Mario Galaxy took its place.