Baron,
Just to be clear...it's a -8, not a -800.
You are correct sir, but I see what prompted your statement. I started a thread called El Ocho Esta Listo. Someone else started a thread called b747-800 certified. When the Mods merged the two threads it made it look as if I called it the -800 since they made me the OP but lifted someone else's title. I've been accused of worse though.
That aside, I seem to recall an internal note going around saying that the number 8 was chosen because it is representative of good luck - in some cultures at least.
Note that the Boeing Company colors changed as well, following the same (good luck) logic.
747-400 House colors:
Google Images
747-8 House colors:
Google Images
The same logic was applied on the 7
E7 which became the 7
87, even though
8 was next after the 7
77.