By looking at what the real Cave Johnson created; a company making shower curtains to a company that makes diet yogurt to a company that makes the worlds most powerful AI ever created, i would not think that i am smarter that Cave Johnson. But since you are talking about Minecraft Cave Johnson, it would be Mojang. Notch started with a small cave game, then moved on with the survival aspecta and then more employees came in and continued on with what Notch left with. They do weekly tests we can attend, just such as what GLaDOS may be doing right now.
I am not smarter that the Minecraft Cave Johnson AKA Mojang. I am smart to thank them for what they have done.
Edit:
Ah fuck, i always get ninja'd. Well i like the story i wrote anyways.